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	$199.49	5.372%	$210.2066	$210.21	$210.20	$210.20
Purchase #2	$242.36	3.141%	$249.9725	$249.97	$249.95	$250.00
Purchase #3	$232.81	12.719%	$262.4211	$262.42	$262.40	$262.40
Purchase #4	$78.45	12.242%	$88.0538	$88.05	$88.05	$88.10
Purchase #5	$64.54	3.733%	$66.9493	$66.95	$66.95	$66.90
Purchase #6	$95.62	5.519%	$100.8973	$100.90	$100.90	$100.90
Purchase #7	$36.56	10.797%	$40.5074	$40.51	$40.50	$40.50
7 purchase totals =	$949.83		$1,019.0080	$1,019.01	$1,018.95	$1,019.00