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	$76.58	10.539%	$84.6508	$84.65	$84.65	$84.70
Purchase #2	$155.98	3.607%	$161.6062	$161.61	$161.60	$161.60
Purchase #3	$169.83	13.734%	$193.1545	$193.15	$193.15	$193.20
Purchase #4	$132.44	3.389%	$136.9284	$136.93	$136.95	$136.90
Purchase #5	$110.25	11.709%	$123.1592	$123.16	$123.15	$123.20
Purchase #6	$98.41	7.241%	$105.5359	$105.54	$105.55	$105.50
Purchase #7	$118.52	4.253%	$123.5607	$123.56	$123.55	$123.60
7 purchase totals =	$862.01		$928.5957	$928.60	$928.60	$928.70