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	$111.31	11.467%	$124.0739	$124.07	$124.05	$124.10
Purchase #2	$70.80	7.817%	$76.3344	$76.33	$76.35	$76.30
Purchase #3	$58.42	10.109%	$64.3257	$64.33	$64.35	$64.30
Purchase #4	$9.74	5.546%	$10.2802	$10.28	$10.30	$10.30
Purchase #5	$235.42	7.668%	$253.472	$253.47	$253.45	$253.50
Purchase #6	$185.69	3.307%	$191.8308	$191.83	$191.85	$191.80
Purchase #7	$99.71	13.560%	$113.2307	$113.23	$113.25	$113.20
7 purchase totals =	$771.09		$833.5477	$833.54	$833.60	$833.50