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	$105.44	5.657%	$111.4047	$111.40	$111.40	$111.40
Purchase #2	$104.70	6.666%	$111.6793	$111.68	$111.70	$111.70
Purchase #3	$146.51	7.394%	$157.3429	$157.34	$157.35	$157.30
Purchase #4	$127.73	10.456%	$141.0854	$141.09	$141.10	$141.10
Purchase #5	$248.60	7.593%	$267.4762	$267.48	$267.50	$267.50
Purchase #6	$129.53	7.434%	$139.1593	$139.16	$139.15	$139.20
Purchase #7	$195.95	9.556%	$214.675	$214.68	$214.70	$214.70
7 purchase totals =	$1,058.46		$1,142.8228	$1,142.83	$1,142.90	$1,142.90