Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$153.31	5.815%	$162.225	$162.23	$162.25	$162.20
Purchase #2	$135.85	6.413%	$144.5621	$144.56	$144.55	$144.60
Purchase #3	$112.31	3.431%	$116.1634	$116.16	$116.15	$116.20
Purchase #4	$200.57	7.356%	$215.3239	$215.32	$215.30	$215.30
Purchase #5	$194.31	9.748%	$213.2513	$213.25	$213.25	$213.30
Purchase #6	$145.68	7.233%	$156.217	$156.22	$156.20	$156.20
Purchase #7	$165.67	3.786%	$171.9423	$171.94	$171.95	$171.90
7 purchase totals =	$1,107.70		$1,179.6850	$1,179.68	$1,179.65	$1,179.70