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	$94.62	11.675%	$105.6669	$105.67	$105.65	$105.70
Purchase #2	$47.82	6.417%	$50.8886	$50.89	$50.90	$50.90
Purchase #3	$227.65	12.231%	$255.4939	$255.49	$255.50	$255.50
Purchase #4	$32.94	12.380%	$37.018	$37.02	$37.00	$37.00
Purchase #5	$222.88	9.528%	$244.116	$244.12	$244.10	$244.10
Purchase #6	$45.72	10.579%	$50.5567	$50.56	$50.55	$50.60
Purchase #7	$214.65	7.775%	$231.339	$231.34	$231.35	$231.30
7 purchase totals =	$886.28		$975.0791	$975.09	$975.05	$975.10