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	$131.43	12.433%	$147.7707	$147.77	$147.75	$147.80
Purchase #2	$22.36	6.804%	$23.8814	$23.88	$23.90	$23.90
Purchase #3	$143.62	5.752%	$151.881	$151.88	$151.90	$151.90
Purchase #4	$37.75	10.165%	$41.5873	$41.59	$41.60	$41.60
Purchase #5	$25.92	13.634%	$29.4539	$29.45	$29.45	$29.50
Purchase #6	$123.47	5.874%	$130.7226	$130.72	$130.70	$130.70
Purchase #7	$220.84	10.861%	$244.8254	$244.83	$244.85	$244.80
7 purchase totals =	$705.39		$770.1223	$770.12	$770.15	$770.20