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	$41.26	13.203%	$46.7076	$46.71	$46.70	$46.70
Purchase #2	$28.96	10.564%	$32.0193	$32.02	$32.00	$32.00
Purchase #3	$177.76	10.735%	$196.8425	$196.84	$196.85	$196.80
Purchase #4	$230.59	4.742%	$241.5246	$241.52	$241.50	$241.50
Purchase #5	$190.95	6.760%	$203.8582	$203.86	$203.85	$203.90
Purchase #6	$10.38	12.690%	$11.6972	$11.70	$11.70	$11.70
Purchase #7	$77.89	4.647%	$81.5095	$81.51	$81.50	$81.50
7 purchase totals =	$757.79		$814.1589	$814.16	$814.10	$814.10