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	$167.59	12.419%	$188.403	$188.40	$188.40	$188.40
Purchase #2	$89.67	6.186%	$95.217	$95.22	$95.20	$95.20
Purchase #3	$180.85	10.807%	$200.3945	$200.39	$200.40	$200.40
Purchase #4	$153.38	8.697%	$166.7195	$166.72	$166.70	$166.70
Purchase #5	$43.76	13.831%	$49.8124	$49.81	$49.80	$49.80
Purchase #6	$83.41	10.384%	$92.0713	$92.07	$92.05	$92.10
Purchase #7	$99.31	12.394%	$111.6185	$111.62	$111.60	$111.60
7 purchase totals =	$817.97		$904.2362	$904.23	$904.15	$904.20