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	$78.64	6.462%	$83.7217	$83.72	$83.70	$83.70
Purchase #2	$35.92	4.671%	$37.5978	$37.60	$37.60	$37.60
Purchase #3	$189.84	9.641%	$208.1425	$208.14	$208.15	$208.10
Purchase #4	$137.64	6.678%	$146.8316	$146.83	$146.85	$146.80
Purchase #5	$69.80	9.669%	$76.549	$76.55	$76.55	$76.50
Purchase #6	$84.58	8.504%	$91.7727	$91.77	$91.75	$91.80
Purchase #7	$165.48	10.187%	$182.3374	$182.34	$182.35	$182.30
7 purchase totals =	$761.90		$826.9527	$826.95	$826.95	$826.80