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	$216.99	5.504%	$228.9331	$228.93	$228.95	$228.90
Purchase #2	$40.90	12.736%	$46.109	$46.11	$46.10	$46.10
Purchase #3	$51.74	13.170%	$58.5542	$58.55	$58.55	$58.60
Purchase #4	$94.81	11.214%	$105.442	$105.44	$105.45	$105.40
Purchase #5	$16.45	11.333%	$18.3143	$18.31	$18.30	$18.30
Purchase #6	$32.29	4.629%	$33.7847	$33.78	$33.80	$33.80
Purchase #7	$249.65	10.178%	$275.0594	$275.06	$275.05	$275.10
7 purchase totals =	$702.83		$766.1967	$766.18	$766.20	$766.20