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	$57.36	8.659%	$62.3268	$62.33	$62.35	$62.30
Purchase #2	$32.96	13.334%	$37.3549	$37.35	$37.35	$37.40
Purchase #3	$55.74	4.809%	$58.4205	$58.42	$58.40	$58.40
Purchase #4	$154.72	7.459%	$166.2606	$166.26	$166.25	$166.30
Purchase #5	$147.57	5.670%	$155.9372	$155.94	$155.95	$155.90
Purchase #6	$55.34	7.433%	$59.4534	$59.45	$59.45	$59.50
Purchase #7	$172.87	3.603%	$179.0985	$179.10	$179.10	$179.10
7 purchase totals =	$676.56		$718.8519	$718.85	$718.85	$718.90