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	$41.63	10.682%	$46.0769	$46.08	$46.10	$46.10
Purchase #2	$105.78	13.866%	$120.4475	$120.45	$120.45	$120.40
Purchase #3	$182.89	4.827%	$191.7181	$191.72	$191.70	$191.70
Purchase #4	$216.50	8.221%	$234.2985	$234.30	$234.30	$234.30
Purchase #5	$241.48	5.842%	$255.5873	$255.59	$255.60	$255.60
Purchase #6	$53.80	10.198%	$59.2865	$59.29	$59.30	$59.30
Purchase #7	$223.25	3.125%	$230.2266	$230.23	$230.25	$230.20
7 purchase totals =	$1,065.33		$1,137.6414	$1,137.66	$1,137.70	$1,137.60