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	$229.47	5.574%	$242.2607	$242.26	$242.25	$242.30
Purchase #2	$244.31	4.449%	$255.1794	$255.18	$255.20	$255.20
Purchase #3	$36.97	7.841%	$39.8688	$39.87	$39.85	$39.90
Purchase #4	$243.95	7.690%	$262.7098	$262.71	$262.70	$262.70
Purchase #5	$12.57	7.292%	$13.4866	$13.49	$13.50	$13.50
Purchase #6	$33.50	12.592%	$37.7183	$37.72	$37.70	$37.70
Purchase #7	$83.54	13.366%	$94.706	$94.71	$94.70	$94.70
7 purchase totals =	$884.31		$945.9296	$945.94	$945.90	$946.00