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	$199.80	11.578%	$222.9328	$222.93	$222.95	$222.90
Purchase #2	$65.34	8.874%	$71.1383	$71.14	$71.15	$71.10
Purchase #3	$92.40	8.667%	$100.4083	$100.41	$100.40	$100.40
Purchase #4	$61.32	9.833%	$67.3496	$67.35	$67.35	$67.30
Purchase #5	$155.42	6.672%	$165.7896	$165.79	$165.80	$165.80
Purchase #6	$63.96	9.653%	$70.1341	$70.13	$70.15	$70.10
Purchase #7	$18.58	12.500%	$20.9025	$20.90	$20.90	$20.90
7 purchase totals =	$656.82		$718.6552	$718.65	$718.70	$718.50