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	$127.79	7.690%	$137.6171	$137.62	$137.60	$137.60
Purchase #2	$216.33	13.123%	$244.719	$244.72	$244.70	$244.70
Purchase #3	$237.34	6.355%	$252.423	$252.42	$252.40	$252.40
Purchase #4	$95.30	5.802%	$100.8293	$100.83	$100.85	$100.80
Purchase #5	$211.58	5.753%	$223.7522	$223.75	$223.75	$223.80
Purchase #6	$11.26	13.355%	$12.7638	$12.76	$12.75	$12.80
Purchase #7	$37.71	7.364%	$40.487	$40.49	$40.50	$40.50
7 purchase totals =	$937.31		$1,012.5914	$1,012.59	$1,012.55	$1,012.60