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	$246.33	7.785%	$265.5068	$265.51	$265.50	$265.50
Purchase #2	$87.44	3.359%	$90.3771	$90.38	$90.40	$90.40
Purchase #3	$150.52	4.155%	$156.7741	$156.77	$156.75	$156.80
Purchase #4	$77.34	13.420%	$87.719	$87.72	$87.70	$87.70
Purchase #5	$165.55	4.117%	$172.3657	$172.37	$172.35	$172.40
Purchase #6	$57.97	6.246%	$61.5908	$61.59	$61.60	$61.60
Purchase #7	$221.30	5.246%	$232.9094	$232.91	$232.90	$232.90
7 purchase totals =	$1,006.45		$1,067.2429	$1,067.25	$1,067.20	$1,067.30