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	$33.35	3.758%	$34.6033	$34.60	$34.60	$34.60
Purchase #2	$137.96	4.222%	$143.7847	$143.78	$143.80	$143.80
Purchase #3	$237.95	5.606%	$251.2895	$251.29	$251.30	$251.30
Purchase #4	$191.40	3.253%	$197.6262	$197.63	$197.65	$197.60
Purchase #5	$37.37	6.815%	$39.9168	$39.92	$39.90	$39.90
Purchase #6	$74.96	4.823%	$78.5753	$78.58	$78.60	$78.60
Purchase #7	$18.76	11.108%	$20.8439	$20.84	$20.85	$20.80
7 purchase totals =	$731.75		$766.6397	$766.64	$766.70	$766.60