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	$197.69	7.303%	$212.1273	$212.13	$212.15	$212.10
Purchase #2	$17.78	5.863%	$18.8224	$18.82	$18.80	$18.80
Purchase #3	$59.29	8.684%	$64.4387	$64.44	$64.45	$64.40
Purchase #4	$171.59	11.444%	$191.2268	$191.23	$191.25	$191.20
Purchase #5	$56.77	4.411%	$59.2741	$59.27	$59.25	$59.30
Purchase #6	$58.86	3.854%	$61.1285	$61.13	$61.15	$61.10
Purchase #7	$185.48	7.229%	$198.8883	$198.89	$198.90	$198.90
7 purchase totals =	$747.46		$805.9061	$805.91	$805.95	$805.80