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	$244.89	6.474%	$260.7442	$260.74	$260.75	$260.70
Purchase #2	$163.75	4.366%	$170.8993	$170.90	$170.90	$170.90
Purchase #3	$208.92	4.167%	$217.6257	$217.63	$217.65	$217.60
Purchase #4	$59.29	10.603%	$65.5765	$65.58	$65.60	$65.60
Purchase #5	$43.56	4.604%	$45.5655	$45.57	$45.55	$45.60
Purchase #6	$89.89	12.408%	$101.0436	$101.04	$101.05	$101.00
Purchase #7	$75.89	3.861%	$78.8201	$78.82	$78.80	$78.80
7 purchase totals =	$886.19		$940.2749	$940.28	$940.30	$940.20