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	$151.84	4.146%	$158.1353	$158.14	$158.15	$158.10
Purchase #2	$114.53	8.669%	$124.4586	$124.46	$124.45	$124.50
Purchase #3	$29.59	11.434%	$32.9733	$32.97	$32.95	$33.00
Purchase #4	$202.27	11.462%	$225.4542	$225.45	$225.45	$225.50
Purchase #5	$116.45	9.547%	$127.5675	$127.57	$127.55	$127.60
Purchase #6	$36.55	3.731%	$37.9137	$37.91	$37.90	$37.90
Purchase #7	$239.72	7.180%	$256.9319	$256.93	$256.95	$256.90
7 purchase totals =	$890.95		$963.4345	$963.43	$963.40	$963.50