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	$132.60	13.625%	$150.6668	$150.67	$150.65	$150.70
Purchase #2	$140.82	7.436%	$151.2914	$151.29	$151.30	$151.30
Purchase #3	$190.97	8.269%	$206.7613	$206.76	$206.75	$206.80
Purchase #4	$15.63	9.501%	$17.115	$17.12	$17.10	$17.10
Purchase #5	$88.52	12.462%	$99.5514	$99.55	$99.55	$99.60
Purchase #6	$64.29	5.111%	$67.5759	$67.58	$67.60	$67.60
Purchase #7	$33.36	12.603%	$37.5644	$37.56	$37.55	$37.60
7 purchase totals =	$666.19		$730.5262	$730.53	$730.50	$730.70