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	$217.70	3.517%	$225.3565	$225.36	$225.35	$225.40
Purchase #2	$218.27	7.792%	$235.2776	$235.28	$235.30	$235.30
Purchase #3	$55.61	3.455%	$57.5313	$57.53	$57.55	$57.50
Purchase #4	$34.60	6.852%	$36.9708	$36.97	$36.95	$37.00
Purchase #5	$98.84	6.707%	$105.4692	$105.47	$105.45	$105.50
Purchase #6	$78.90	5.857%	$83.5212	$83.52	$83.50	$83.50
Purchase #7	$83.84	9.117%	$91.4837	$91.48	$91.50	$91.50
7 purchase totals =	$787.76		$835.6103	$835.61	$835.60	$835.70