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	$231.96	13.155%	$262.4743	$262.47	$262.45	$262.50
Purchase #2	$159.73	3.413%	$165.1816	$165.18	$165.20	$165.20
Purchase #3	$93.57	6.577%	$99.7241	$99.72	$99.70	$99.70
Purchase #4	$50.88	8.371%	$55.1392	$55.14	$55.15	$55.10
Purchase #5	$7.40	5.109%	$7.7781	$7.78	$7.80	$7.80
Purchase #6	$211.87	4.847%	$222.1393	$222.14	$222.15	$222.10
Purchase #7	$41.43	10.530%	$45.7926	$45.79	$45.80	$45.80
7 purchase totals =	$796.84		$858.2292	$858.22	$858.25	$858.20