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	$230.89	10.602%	$255.369	$255.37	$255.35	$255.40
Purchase #2	$138.38	4.268%	$144.2861	$144.29	$144.30	$144.30
Purchase #3	$235.52	4.465%	$246.036	$246.04	$246.05	$246.00
Purchase #4	$203.36	13.847%	$231.5193	$231.52	$231.50	$231.50
Purchase #5	$82.31	10.310%	$90.7962	$90.80	$90.80	$90.80
Purchase #6	$212.26	6.150%	$225.314	$225.31	$225.30	$225.30
Purchase #7	$232.47	12.138%	$260.6872	$260.69	$260.70	$260.70
7 purchase totals =	$1,335.19		$1,454.0078	$1,454.02	$1,454.00	$1,454.00