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	$133.68	9.433%	$146.29	$146.29	$146.30	$146.30
Purchase #2	$78.59	5.743%	$83.1034	$83.10	$83.10	$83.10
Purchase #3	$156.54	4.780%	$164.0226	$164.02	$164.00	$164.00
Purchase #4	$139.64	5.539%	$147.3747	$147.37	$147.35	$147.40
Purchase #5	$134.60	6.816%	$143.7743	$143.77	$143.75	$143.80
Purchase #6	$62.80	5.168%	$66.0455	$66.05	$66.05	$66.00
Purchase #7	$119.76	4.275%	$124.8797	$124.88	$124.90	$124.90
7 purchase totals =	$825.61		$875.4902	$875.48	$875.45	$875.50