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	$124.47	10.339%	$137.339	$137.34	$137.35	$137.30
Purchase #2	$9.37	12.447%	$10.5363	$10.54	$10.55	$10.50
Purchase #3	$65.30	10.145%	$71.9247	$71.92	$71.90	$71.90
Purchase #4	$149.25	6.731%	$159.296	$159.30	$159.30	$159.30
Purchase #5	$59.57	11.699%	$66.5391	$66.54	$66.55	$66.50
Purchase #6	$121.69	7.340%	$130.622	$130.62	$130.60	$130.60
Purchase #7	$33.44	10.866%	$37.0736	$37.07	$37.05	$37.10
7 purchase totals =	$563.09		$613.3307	$613.33	$613.30	$613.20