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	$83.71	8.493%	$90.8195	$90.82	$90.80	$90.80
Purchase #2	$81.50	4.588%	$85.2392	$85.24	$85.25	$85.20
Purchase #3	$15.53	9.742%	$17.0429	$17.04	$17.05	$17.00
Purchase #4	$11.44	6.313%	$12.1622	$12.16	$12.15	$12.20
Purchase #5	$86.91	8.540%	$94.3321	$94.33	$94.35	$94.30
Purchase #6	$18.59	9.129%	$20.2871	$20.29	$20.30	$20.30
Purchase #7	$160.71	11.827%	$179.7172	$179.72	$179.70	$179.70
7 purchase totals =	$458.39		$499.6002	$499.60	$499.60	$499.50