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	$177.31	10.625%	$196.1492	$196.15	$196.15	$196.10
Purchase #2	$240.40	7.613%	$258.7017	$258.70	$258.70	$258.70
Purchase #3	$74.28	12.183%	$83.3295	$83.33	$83.35	$83.30
Purchase #4	$66.49	11.391%	$74.0639	$74.06	$74.05	$74.10
Purchase #5	$37.55	4.482%	$39.233	$39.23	$39.25	$39.20
Purchase #6	$220.73	9.443%	$241.5735	$241.57	$241.55	$241.60
Purchase #7	$92.34	7.850%	$99.5887	$99.59	$99.60	$99.60
7 purchase totals =	$909.10		$992.6395	$992.63	$992.65	$992.60