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	$131.78	6.758%	$140.6857	$140.69	$140.70	$140.70
Purchase #2	$32.41	4.594%	$33.8989	$33.90	$33.90	$33.90
Purchase #3	$173.86	4.525%	$181.7272	$181.73	$181.75	$181.70
Purchase #4	$116.86	7.325%	$125.42	$125.42	$125.40	$125.40
Purchase #5	$176.59	12.767%	$199.1352	$199.14	$199.15	$199.10
Purchase #6	$241.88	13.133%	$273.6461	$273.65	$273.65	$273.60
Purchase #7	$22.43	8.484%	$24.333	$24.33	$24.35	$24.30
7 purchase totals =	$895.81		$978.8461	$978.86	$978.90	$978.70