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	$90.53	4.300%	$94.4228	$94.42	$94.40	$94.40
Purchase #2	$200.48	4.536%	$209.5738	$209.57	$209.55	$209.60
Purchase #3	$72.50	4.552%	$75.8002	$75.80	$75.80	$75.80
Purchase #4	$124.90	11.732%	$139.5533	$139.55	$139.55	$139.60
Purchase #5	$88.54	4.601%	$92.6137	$92.61	$92.60	$92.60
Purchase #6	$131.53	3.493%	$136.1243	$136.12	$136.10	$136.10
Purchase #7	$126.38	9.142%	$137.9337	$137.93	$137.95	$137.90
7 purchase totals =	$834.86		$886.0218	$886.00	$885.95	$886.00