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	$41.53	9.425%	$45.4442	$45.44	$45.45	$45.40
Purchase #2	$111.34	6.130%	$118.1651	$118.17	$118.15	$118.20
Purchase #3	$37.56	11.219%	$41.7739	$41.77	$41.75	$41.80
Purchase #4	$245.51	3.468%	$254.0243	$254.02	$254.00	$254.00
Purchase #5	$171.34	10.164%	$188.755	$188.76	$188.75	$188.80
Purchase #6	$83.29	8.661%	$90.5037	$90.50	$90.50	$90.50
Purchase #7	$160.29	7.806%	$172.8022	$172.80	$172.80	$172.80
7 purchase totals =	$850.86		$911.4684	$911.46	$911.40	$911.50