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	$69.66	11.719%	$77.8235	$77.82	$77.80	$77.80
Purchase #2	$126.54	3.266%	$130.6728	$130.67	$130.65	$130.70
Purchase #3	$176.69	11.168%	$196.4227	$196.42	$196.40	$196.40
Purchase #4	$14.26	11.822%	$15.9458	$15.95	$15.95	$15.90
Purchase #5	$53.46	13.519%	$60.6873	$60.69	$60.70	$60.70
Purchase #6	$55.25	7.819%	$59.57	$59.57	$59.55	$59.60
Purchase #7	$107.95	3.143%	$111.3429	$111.34	$111.35	$111.30
7 purchase totals =	$603.81		$652.4650	$652.46	$652.40	$652.40