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	$149.31	10.835%	$165.4877	$165.49	$165.50	$165.50
Purchase #2	$159.72	10.633%	$176.703	$176.70	$176.70	$176.70
Purchase #3	$120.85	8.139%	$130.686	$130.69	$130.70	$130.70
Purchase #4	$92.72	13.798%	$105.5135	$105.51	$105.50	$105.50
Purchase #5	$32.67	13.308%	$37.0177	$37.02	$37.00	$37.00
Purchase #6	$37.29	11.341%	$41.5191	$41.52	$41.50	$41.50
Purchase #7	$72.38	10.674%	$80.1058	$80.11	$80.10	$80.10
7 purchase totals =	$664.94		$737.0328	$737.04	$737.00	$737.00