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	$185.29	8.267%	$200.6079	$200.61	$200.60	$200.60
Purchase #2	$209.73	4.833%	$219.8663	$219.87	$219.85	$219.90
Purchase #3	$83.60	6.270%	$88.8417	$88.84	$88.85	$88.80
Purchase #4	$42.75	7.239%	$45.8447	$45.84	$45.85	$45.80
Purchase #5	$129.63	7.363%	$139.1747	$139.17	$139.15	$139.20
Purchase #6	$10.59	3.272%	$10.9365	$10.94	$10.95	$10.90
Purchase #7	$155.51	6.485%	$165.5948	$165.59	$165.60	$165.60
7 purchase totals =	$817.10		$870.8666	$870.86	$870.85	$870.80