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	$50.60	3.706%	$52.4752	$52.48	$52.50	$52.50
Purchase #2	$48.46	3.643%	$50.2254	$50.23	$50.25	$50.20
Purchase #3	$220.94	10.784%	$244.7662	$244.77	$244.75	$244.80
Purchase #4	$119.94	13.678%	$136.3454	$136.35	$136.35	$136.30
Purchase #5	$229.87	11.168%	$255.5419	$255.54	$255.55	$255.50
Purchase #6	$174.30	4.694%	$182.4816	$182.48	$182.50	$182.50
Purchase #7	$24.39	4.643%	$25.5224	$25.52	$25.50	$25.50
7 purchase totals =	$868.50		$947.3581	$947.37	$947.40	$947.30