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	$208.65	3.154%	$215.2308	$215.23	$215.25	$215.20
Purchase #2	$37.64	13.186%	$42.6032	$42.60	$42.60	$42.60
Purchase #3	$125.40	11.730%	$140.1094	$140.11	$140.10	$140.10
Purchase #4	$88.73	13.678%	$100.8665	$100.87	$100.85	$100.90
Purchase #5	$77.53	7.528%	$83.3665	$83.37	$83.35	$83.40
Purchase #6	$59.52	5.744%	$62.9388	$62.94	$62.95	$62.90
Purchase #7	$190.57	11.530%	$212.5427	$212.54	$212.55	$212.50
7 purchase totals =	$788.04		$857.6579	$857.66	$857.65	$857.60