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	$130.92	12.500%	$147.285	$147.29	$147.30	$147.30
Purchase #2	$135.41	11.301%	$150.7127	$150.71	$150.70	$150.70
Purchase #3	$126.93	7.311%	$136.2099	$136.21	$136.20	$136.20
Purchase #4	$89.77	4.103%	$93.4533	$93.45	$93.45	$93.50
Purchase #5	$148.38	9.456%	$162.4108	$162.41	$162.40	$162.40
Purchase #6	$248.45	10.643%	$274.8925	$274.89	$274.90	$274.90
Purchase #7	$140.34	4.248%	$146.3016	$146.30	$146.30	$146.30
7 purchase totals =	$1,020.20		$1,111.2658	$1,111.26	$1,111.25	$1,111.30