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	$83.35	4.785%	$87.3383	$87.34	$87.35	$87.30
Purchase #2	$241.29	13.810%	$274.6121	$274.61	$274.60	$274.60
Purchase #3	$89.82	4.857%	$94.1826	$94.18	$94.20	$94.20
Purchase #4	$152.25	8.521%	$165.2232	$165.22	$165.20	$165.20
Purchase #5	$139.63	6.790%	$149.1109	$149.11	$149.10	$149.10
Purchase #6	$147.38	8.734%	$160.2522	$160.25	$160.25	$160.30
Purchase #7	$227.51	12.127%	$255.1001	$255.10	$255.10	$255.10
7 purchase totals =	$1,081.23		$1,185.8194	$1,185.81	$1,185.80	$1,185.80