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	$248.97	3.673%	$258.1147	$258.11	$258.10	$258.10
Purchase #2	$145.87	9.362%	$159.5263	$159.53	$159.55	$159.50
Purchase #3	$111.58	13.265%	$126.3811	$126.38	$126.40	$126.40
Purchase #4	$110.72	11.492%	$123.4439	$123.44	$123.45	$123.40
Purchase #5	$215.51	3.167%	$222.3352	$222.34	$222.35	$222.30
Purchase #6	$206.93	8.817%	$225.175	$225.18	$225.20	$225.20
Purchase #7	$161.88	6.353%	$172.1642	$172.16	$172.15	$172.20
7 purchase totals =	$1,201.46		$1,287.1404	$1,287.14	$1,287.20	$1,287.10