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	$140.82	7.566%	$151.4744	$151.47	$151.45	$151.50
Purchase #2	$66.78	6.816%	$71.3317	$71.33	$71.35	$71.30
Purchase #3	$91.44	12.328%	$102.7127	$102.71	$102.70	$102.70
Purchase #4	$6.69	12.164%	$7.5038	$7.50	$7.50	$7.50
Purchase #5	$212.90	4.701%	$222.9084	$222.91	$222.90	$222.90
Purchase #6	$18.31	7.733%	$19.7259	$19.73	$19.75	$19.70
Purchase #7	$219.33	11.300%	$244.1143	$244.11	$244.10	$244.10
7 purchase totals =	$756.27		$819.7712	$819.76	$819.75	$819.70