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	$48.62	4.201%	$50.6625	$50.66	$50.65	$50.70
Purchase #2	$61.41	8.394%	$66.5648	$66.56	$66.55	$66.60
Purchase #3	$146.59	6.130%	$155.576	$155.58	$155.60	$155.60
Purchase #4	$34.93	13.375%	$39.6019	$39.60	$39.60	$39.60
Purchase #5	$188.37	3.197%	$194.3922	$194.39	$194.40	$194.40
Purchase #6	$131.30	8.657%	$142.6666	$142.67	$142.65	$142.70
Purchase #7	$48.95	13.298%	$55.4594	$55.46	$55.45	$55.50
7 purchase totals =	$660.17		$704.9234	$704.92	$704.90	$705.10