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	$211.61	4.206%	$220.5103	$220.51	$220.50	$220.50
Purchase #2	$215.86	12.552%	$242.9547	$242.95	$242.95	$243.00
Purchase #3	$131.53	6.362%	$139.8979	$139.90	$139.90	$139.90
Purchase #4	$79.83	7.512%	$85.8268	$85.83	$85.85	$85.80
Purchase #5	$59.94	10.500%	$66.2337	$66.23	$66.25	$66.20
Purchase #6	$48.80	3.488%	$50.5021	$50.50	$50.50	$50.50
Purchase #7	$235.49	13.436%	$267.1304	$267.13	$267.15	$267.10
7 purchase totals =	$983.06		$1,073.0559	$1,073.05	$1,073.10	$1,073.00