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	$215.33	4.382%	$224.7658	$224.77	$224.75	$224.80
Purchase #2	$76.54	12.818%	$86.3509	$86.35	$86.35	$86.40
Purchase #3	$62.90	10.443%	$69.4686	$69.47	$69.45	$69.50
Purchase #4	$40.46	7.569%	$43.5224	$43.52	$43.50	$43.50
Purchase #5	$53.68	3.603%	$55.6141	$55.61	$55.60	$55.60
Purchase #6	$201.38	3.858%	$209.1492	$209.15	$209.15	$209.10
Purchase #7	$67.32	11.339%	$74.9534	$74.95	$74.95	$75.00
7 purchase totals =	$717.61		$763.8244	$763.82	$763.75	$763.90