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	$196.54	4.496%	$205.3764	$205.38	$205.40	$205.40
Purchase #2	$216.37	7.466%	$232.5242	$232.52	$232.50	$232.50
Purchase #3	$30.98	4.180%	$32.275	$32.28	$32.30	$32.30
Purchase #4	$63.27	4.238%	$65.9514	$65.95	$65.95	$66.00
Purchase #5	$199.38	11.533%	$222.3745	$222.37	$222.35	$222.40
Purchase #6	$184.55	10.151%	$203.2837	$203.28	$203.30	$203.30
Purchase #7	$242.66	5.706%	$256.5062	$256.51	$256.50	$256.50
7 purchase totals =	$1,133.75		$1,218.2914	$1,218.29	$1,218.30	$1,218.40