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	$216.98	3.458%	$224.4832	$224.48	$224.50	$224.50
Purchase #2	$134.35	11.873%	$150.3014	$150.30	$150.30	$150.30
Purchase #3	$138.54	7.259%	$148.5966	$148.60	$148.60	$148.60
Purchase #4	$172.58	13.489%	$195.8593	$195.86	$195.85	$195.90
Purchase #5	$200.41	11.157%	$222.7697	$222.77	$222.75	$222.80
Purchase #6	$46.33	8.698%	$50.3598	$50.36	$50.35	$50.40
Purchase #7	$62.80	13.296%	$71.1499	$71.15	$71.15	$71.10
7 purchase totals =	$971.99		$1,063.5199	$1,063.52	$1,063.50	$1,063.60