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	$84.91	10.869%	$94.1389	$94.14	$94.15	$94.10
Purchase #2	$70.71	7.590%	$76.0769	$76.08	$76.10	$76.10
Purchase #3	$144.35	9.631%	$158.2523	$158.25	$158.25	$158.30
Purchase #4	$151.56	9.430%	$165.8521	$165.85	$165.85	$165.90
Purchase #5	$33.98	11.411%	$37.8575	$37.86	$37.85	$37.90
Purchase #6	$40.96	5.555%	$43.2353	$43.24	$43.25	$43.20
Purchase #7	$86.66	12.243%	$97.2698	$97.27	$97.25	$97.30
7 purchase totals =	$613.13		$672.6828	$672.69	$672.70	$672.80