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	$53.97	10.343%	$59.5521	$59.55	$59.55	$59.60
Purchase #2	$223.59	10.409%	$246.8635	$246.86	$246.85	$246.90
Purchase #3	$87.73	6.750%	$93.6518	$93.65	$93.65	$93.70
Purchase #4	$82.96	8.769%	$90.2348	$90.23	$90.25	$90.20
Purchase #5	$223.81	6.382%	$238.0936	$238.09	$238.10	$238.10
Purchase #6	$60.77	11.530%	$67.7768	$67.78	$67.80	$67.80
Purchase #7	$139.69	3.290%	$144.2858	$144.29	$144.30	$144.30
7 purchase totals =	$872.52		$940.4584	$940.45	$940.50	$940.60