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	$50.48	7.244%	$54.1368	$54.14	$54.15	$54.10
Purchase #2	$247.85	6.457%	$263.8537	$263.85	$263.85	$263.90
Purchase #3	$181.57	10.230%	$200.1446	$200.14	$200.15	$200.10
Purchase #4	$88.35	13.293%	$100.0944	$100.09	$100.10	$100.10
Purchase #5	$195.96	7.567%	$210.7883	$210.79	$210.80	$210.80
Purchase #6	$124.71	12.717%	$140.5694	$140.57	$140.55	$140.60
Purchase #7	$60.33	11.388%	$67.2004	$67.20	$67.20	$67.20
7 purchase totals =	$949.25		$1,036.7876	$1,036.78	$1,036.80	$1,036.80