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	$87.98	13.327%	$99.7051	$99.71	$99.70	$99.70
Purchase #2	$88.67	7.752%	$95.5437	$95.54	$95.55	$95.50
Purchase #3	$99.34	3.309%	$102.6272	$102.63	$102.65	$102.60
Purchase #4	$157.98	9.215%	$172.5379	$172.54	$172.55	$172.50
Purchase #5	$221.80	13.243%	$251.173	$251.17	$251.15	$251.20
Purchase #6	$190.30	6.763%	$203.17	$203.17	$203.15	$203.20
Purchase #7	$102.64	11.526%	$114.4703	$114.47	$114.45	$114.50
7 purchase totals =	$948.71		$1,039.2272	$1,039.23	$1,039.20	$1,039.20