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	$38.82	10.628%	$42.9458	$42.95	$42.95	$42.90
Purchase #2	$59.32	3.323%	$61.2912	$61.29	$61.30	$61.30
Purchase #3	$126.92	10.794%	$140.6197	$140.62	$140.60	$140.60
Purchase #4	$150.25	6.681%	$160.2882	$160.29	$160.30	$160.30
Purchase #5	$224.55	9.382%	$245.6173	$245.62	$245.60	$245.60
Purchase #6	$117.88	3.543%	$122.0565	$122.06	$122.05	$122.10
Purchase #7	$224.94	12.689%	$253.4826	$253.48	$253.50	$253.50
7 purchase totals =	$942.68		$1,026.3013	$1,026.31	$1,026.30	$1,026.30