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	$136.37	11.463%	$152.0021	$152.00	$152.00	$152.00
Purchase #2	$136.94	5.183%	$144.0376	$144.04	$144.05	$144.00
Purchase #3	$155.73	11.393%	$173.4723	$173.47	$173.45	$173.50
Purchase #4	$57.46	7.407%	$61.7161	$61.72	$61.70	$61.70
Purchase #5	$192.96	11.503%	$215.1562	$215.16	$215.15	$215.20
Purchase #6	$229.55	7.742%	$247.3218	$247.32	$247.30	$247.30
Purchase #7	$140.65	5.577%	$148.4941	$148.49	$148.50	$148.50
7 purchase totals =	$1,049.66		$1,142.2002	$1,142.20	$1,142.15	$1,142.20