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	$116.48	10.684%	$128.9247	$128.92	$128.90	$128.90
Purchase #2	$157.69	9.318%	$172.3836	$172.38	$172.40	$172.40
Purchase #3	$38.67	6.427%	$41.1553	$41.16	$41.15	$41.20
Purchase #4	$141.71	6.702%	$151.2074	$151.21	$151.20	$151.20
Purchase #5	$179.61	8.870%	$195.5414	$195.54	$195.55	$195.50
Purchase #6	$40.89	11.104%	$45.4304	$45.43	$45.45	$45.40
Purchase #7	$84.42	7.397%	$90.6645	$90.66	$90.65	$90.70
7 purchase totals =	$759.47		$825.3073	$825.30	$825.30	$825.30