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	$127.63	4.496%	$133.3682	$133.37	$133.35	$133.40
Purchase #2	$50.67	10.859%	$56.1723	$56.17	$56.15	$56.20
Purchase #3	$194.87	8.259%	$210.9643	$210.96	$210.95	$211.00
Purchase #4	$60.76	11.730%	$67.8871	$67.89	$67.90	$67.90
Purchase #5	$141.29	9.172%	$154.2491	$154.25	$154.25	$154.20
Purchase #6	$88.65	11.103%	$98.4928	$98.49	$98.50	$98.50
Purchase #7	$155.61	11.841%	$174.0358	$174.04	$174.05	$174.00
7 purchase totals =	$819.48		$895.1696	$895.17	$895.15	$895.20