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	$226.34	12.709%	$255.1056	$255.11	$255.10	$255.10
Purchase #2	$245.56	10.727%	$271.9012	$271.90	$271.90	$271.90
Purchase #3	$229.68	11.532%	$256.1667	$256.17	$256.15	$256.20
Purchase #4	$168.89	13.778%	$192.1597	$192.16	$192.15	$192.20
Purchase #5	$157.40	9.577%	$172.4742	$172.47	$172.45	$172.50
Purchase #6	$182.45	4.818%	$191.2404	$191.24	$191.25	$191.20
Purchase #7	$110.48	5.342%	$116.3818	$116.38	$116.40	$116.40
7 purchase totals =	$1,320.80		$1,455.4296	$1,455.43	$1,455.40	$1,455.50