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	$139.83	7.207%	$149.9075	$149.91	$149.90	$149.90
Purchase #2	$130.30	13.722%	$148.1798	$148.18	$148.20	$148.20
Purchase #3	$139.83	8.629%	$151.8959	$151.90	$151.90	$151.90
Purchase #4	$63.78	9.786%	$70.0215	$70.02	$70.00	$70.00
Purchase #5	$199.70	8.464%	$216.6026	$216.60	$216.60	$216.60
Purchase #6	$161.74	7.356%	$173.6376	$173.64	$173.65	$173.60
Purchase #7	$99.55	11.778%	$111.275	$111.28	$111.30	$111.30
7 purchase totals =	$934.73		$1,021.5199	$1,021.53	$1,021.55	$1,021.50