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	$220.35	3.345%	$227.7207	$227.72	$227.70	$227.70
Purchase #2	$104.31	13.610%	$118.5066	$118.51	$118.50	$118.50
Purchase #3	$97.80	10.731%	$108.2949	$108.29	$108.30	$108.30
Purchase #4	$122.35	7.822%	$131.9202	$131.92	$131.90	$131.90
Purchase #5	$170.86	7.790%	$184.17	$184.17	$184.15	$184.20
Purchase #6	$28.77	11.858%	$32.1815	$32.18	$32.20	$32.20
Purchase #7	$151.52	13.815%	$172.4525	$172.45	$172.45	$172.50
7 purchase totals =	$895.96		$975.2464	$975.24	$975.20	$975.30