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	$214.76	3.795%	$222.9101	$222.91	$222.90	$222.90
Purchase #2	$98.89	5.692%	$104.5188	$104.52	$104.50	$104.50
Purchase #3	$179.25	8.709%	$194.8609	$194.86	$194.85	$194.90
Purchase #4	$6.86	11.733%	$7.6649	$7.66	$7.65	$7.70
Purchase #5	$235.43	11.149%	$261.6781	$261.68	$261.70	$261.70
Purchase #6	$159.39	7.281%	$170.9952	$171.00	$171.00	$171.00
Purchase #7	$108.67	6.606%	$115.8487	$115.85	$115.85	$115.80
7 purchase totals =	$1,003.25		$1,078.4767	$1,078.48	$1,078.45	$1,078.50