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	$34.47	7.711%	$37.128	$37.13	$37.15	$37.10
Purchase #2	$65.62	10.323%	$72.394	$72.39	$72.40	$72.40
Purchase #3	$37.60	11.491%	$41.9206	$41.92	$41.90	$41.90
Purchase #4	$88.39	8.108%	$95.5567	$95.56	$95.55	$95.60
Purchase #5	$226.29	9.849%	$248.5773	$248.58	$248.60	$248.60
Purchase #6	$133.64	13.532%	$151.7242	$151.72	$151.70	$151.70
Purchase #7	$37.61	3.150%	$38.7947	$38.79	$38.80	$38.80
7 purchase totals =	$623.62		$686.0955	$686.09	$686.10	$686.10