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	$82.87	13.588%	$94.1304	$94.13	$94.15	$94.10
Purchase #2	$77.41	10.694%	$85.6882	$85.69	$85.70	$85.70
Purchase #3	$133.33	8.680%	$144.903	$144.90	$144.90	$144.90
Purchase #4	$94.43	11.762%	$105.5369	$105.54	$105.55	$105.50
Purchase #5	$111.68	4.807%	$117.0485	$117.05	$117.05	$117.00
Purchase #6	$179.44	5.517%	$189.3397	$189.34	$189.35	$189.30
Purchase #7	$30.57	10.725%	$33.8486	$33.85	$33.85	$33.80
7 purchase totals =	$709.73		$770.4953	$770.50	$770.55	$770.30