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	$159.46	12.776%	$179.8326	$179.83	$179.85	$179.80
Purchase #2	$66.34	7.449%	$71.2817	$71.28	$71.30	$71.30
Purchase #3	$72.74	6.446%	$77.4288	$77.43	$77.45	$77.40
Purchase #4	$121.71	6.610%	$129.755	$129.76	$129.75	$129.80
Purchase #5	$161.84	5.841%	$171.2931	$171.29	$171.30	$171.30
Purchase #6	$66.37	9.588%	$72.7336	$72.73	$72.75	$72.70
Purchase #7	$193.72	7.485%	$208.2199	$208.22	$208.20	$208.20
7 purchase totals =	$842.18		$910.5447	$910.54	$910.60	$910.50