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	$209.54	7.439%	$225.1277	$225.13	$225.15	$225.10
Purchase #2	$168.45	10.320%	$185.834	$185.83	$185.85	$185.80
Purchase #3	$34.91	4.164%	$36.3637	$36.36	$36.35	$36.40
Purchase #4	$32.80	5.414%	$34.5758	$34.58	$34.60	$34.60
Purchase #5	$143.49	8.259%	$155.3408	$155.34	$155.35	$155.30
Purchase #6	$67.34	7.212%	$72.1966	$72.20	$72.20	$72.20
Purchase #7	$214.90	8.689%	$233.5727	$233.57	$233.55	$233.60
7 purchase totals =	$871.43		$943.0113	$943.01	$943.05	$943.00