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	$155.35	13.222%	$175.8904	$175.89	$175.90	$175.90
Purchase #2	$164.55	12.184%	$184.5988	$184.60	$184.60	$184.60
Purchase #3	$159.97	6.525%	$170.408	$170.41	$170.40	$170.40
Purchase #4	$24.59	10.338%	$27.1321	$27.13	$27.15	$27.10
Purchase #5	$213.68	5.514%	$225.4623	$225.46	$225.45	$225.50
Purchase #6	$208.87	7.791%	$225.1431	$225.14	$225.15	$225.10
Purchase #7	$29.89	8.443%	$32.4136	$32.41	$32.40	$32.40
7 purchase totals =	$956.90		$1,041.0483	$1,041.04	$1,041.05	$1,041.00