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	$85.39	9.759%	$93.7232	$93.72	$93.70	$93.70
Purchase #2	$171.74	10.802%	$190.2914	$190.29	$190.30	$190.30
Purchase #3	$236.74	4.135%	$246.5292	$246.53	$246.55	$246.50
Purchase #4	$241.60	9.488%	$264.523	$264.52	$264.50	$264.50
Purchase #5	$204.67	3.733%	$212.3103	$212.31	$212.30	$212.30
Purchase #6	$69.31	4.651%	$72.5336	$72.53	$72.55	$72.50
Purchase #7	$239.86	5.747%	$253.6448	$253.64	$253.65	$253.60
7 purchase totals =	$1,249.31		$1,333.5555	$1,333.54	$1,333.55	$1,333.40