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	$143.61	4.584%	$150.1931	$150.19	$150.20	$150.20
Purchase #2	$82.60	11.238%	$91.8826	$91.88	$91.90	$91.90
Purchase #3	$224.56	13.258%	$254.3322	$254.33	$254.35	$254.30
Purchase #4	$32.39	4.643%	$33.8939	$33.89	$33.90	$33.90
Purchase #5	$89.66	6.700%	$95.6672	$95.67	$95.65	$95.70
Purchase #6	$96.38	9.414%	$105.4532	$105.45	$105.45	$105.50
Purchase #7	$195.77	9.148%	$213.679	$213.68	$213.70	$213.70
7 purchase totals =	$864.97		$945.1012	$945.09	$945.15	$945.20