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	$168.80	4.361%	$176.1614	$176.16	$176.15	$176.20
Purchase #2	$56.58	9.849%	$62.1526	$62.15	$62.15	$62.20
Purchase #3	$107.88	8.438%	$116.9829	$116.98	$117.00	$117.00
Purchase #4	$162.92	10.568%	$180.1374	$180.14	$180.15	$180.10
Purchase #5	$102.83	8.413%	$111.4811	$111.48	$111.50	$111.50
Purchase #6	$159.73	6.318%	$169.8217	$169.82	$169.80	$169.80
Purchase #7	$176.35	12.717%	$198.7764	$198.78	$198.80	$198.80
7 purchase totals =	$935.09		$1,015.5135	$1,015.51	$1,015.55	$1,015.60