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	$85.86	5.472%	$90.5583	$90.56	$90.55	$90.60
Purchase #2	$247.29	7.383%	$265.5474	$265.55	$265.55	$265.50
Purchase #3	$158.86	9.785%	$174.4045	$174.40	$174.40	$174.40
Purchase #4	$89.80	8.579%	$97.5039	$97.50	$97.50	$97.50
Purchase #5	$69.34	4.778%	$72.6531	$72.65	$72.65	$72.70
Purchase #6	$67.59	10.479%	$74.6728	$74.67	$74.65	$74.70
Purchase #7	$247.74	11.248%	$275.6058	$275.61	$275.60	$275.60
7 purchase totals =	$966.48		$1,050.9458	$1,050.94	$1,050.90	$1,051.00