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	$162.65	4.676%	$170.2555	$170.26	$170.25	$170.30
Purchase #2	$62.97	13.357%	$71.3809	$71.38	$71.40	$71.40
Purchase #3	$66.72	8.677%	$72.5093	$72.51	$72.50	$72.50
Purchase #4	$130.30	7.707%	$140.3422	$140.34	$140.35	$140.30
Purchase #5	$169.45	9.372%	$185.3309	$185.33	$185.35	$185.30
Purchase #6	$17.43	11.419%	$19.4203	$19.42	$19.40	$19.40
Purchase #7	$171.87	13.477%	$195.0329	$195.03	$195.05	$195.00
7 purchase totals =	$781.39		$854.2720	$854.27	$854.30	$854.20