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	$118.67	10.529%	$131.1648	$131.16	$131.15	$131.20
Purchase #2	$157.25	5.471%	$165.8531	$165.85	$165.85	$165.90
Purchase #3	$51.47	4.707%	$53.8927	$53.89	$53.90	$53.90
Purchase #4	$81.53	4.506%	$85.2037	$85.20	$85.20	$85.20
Purchase #5	$160.27	7.472%	$172.2454	$172.25	$172.25	$172.20
Purchase #6	$85.27	3.746%	$88.4642	$88.46	$88.45	$88.50
Purchase #7	$248.64	4.285%	$259.2942	$259.29	$259.30	$259.30
7 purchase totals =	$903.10		$956.1181	$956.10	$956.10	$956.20