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	$197.68	11.830%	$221.0655	$221.07	$221.05	$221.10
Purchase #2	$53.78	11.285%	$59.8491	$59.85	$59.85	$59.80
Purchase #3	$158.56	8.114%	$171.4256	$171.43	$171.45	$171.40
Purchase #4	$28.69	13.422%	$32.5408	$32.54	$32.55	$32.50
Purchase #5	$89.81	3.790%	$93.2138	$93.21	$93.20	$93.20
Purchase #6	$167.32	7.321%	$179.5695	$179.57	$179.55	$179.60
Purchase #7	$63.67	4.540%	$66.5606	$66.56	$66.55	$66.60
7 purchase totals =	$759.51		$824.2249	$824.23	$824.20	$824.20