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	$155.50	6.863%	$166.172	$166.17	$166.15	$166.20
Purchase #2	$44.35	3.353%	$45.8371	$45.84	$45.85	$45.80
Purchase #3	$161.91	8.363%	$175.4505	$175.45	$175.45	$175.50
Purchase #4	$218.93	11.621%	$244.3719	$244.37	$244.35	$244.40
Purchase #5	$106.51	13.356%	$120.7355	$120.74	$120.75	$120.70
Purchase #6	$248.83	6.110%	$264.0335	$264.03	$264.05	$264.00
Purchase #7	$95.77	4.723%	$100.2932	$100.29	$100.30	$100.30
7 purchase totals =	$1,031.80		$1,116.8937	$1,116.89	$1,116.90	$1,116.90