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	$167.83	8.689%	$182.4127	$182.41	$182.40	$182.40
Purchase #2	$69.83	3.547%	$72.3069	$72.31	$72.30	$72.30
Purchase #3	$15.30	11.105%	$16.9991	$17.00	$17.00	$17.00
Purchase #4	$10.35	11.229%	$11.5122	$11.51	$11.50	$11.50
Purchase #5	$117.68	9.249%	$128.5642	$128.56	$128.55	$128.60
Purchase #6	$36.70	13.210%	$41.5481	$41.55	$41.55	$41.50
Purchase #7	$12.73	3.276%	$13.147	$13.15	$13.15	$13.10
7 purchase totals =	$430.42		$466.4902	$466.49	$466.45	$466.40