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	$185.54	12.135%	$208.0553	$208.06	$208.05	$208.10
Purchase #2	$118.49	4.138%	$123.3931	$123.39	$123.40	$123.40
Purchase #3	$76.81	7.128%	$82.285	$82.29	$82.30	$82.30
Purchase #4	$154.80	11.532%	$172.6515	$172.65	$172.65	$172.70
Purchase #5	$69.57	8.335%	$75.3687	$75.37	$75.35	$75.40
Purchase #6	$66.60	8.171%	$72.0419	$72.04	$72.05	$72.00
Purchase #7	$190.88	4.137%	$198.7767	$198.78	$198.80	$198.80
7 purchase totals =	$862.69		$932.5722	$932.58	$932.60	$932.70