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	$132.51	5.822%	$140.2247	$140.22	$140.20	$140.20
Purchase #2	$168.36	3.166%	$173.6903	$173.69	$173.70	$173.70
Purchase #3	$40.54	4.746%	$42.464	$42.46	$42.45	$42.50
Purchase #4	$137.50	5.785%	$145.4544	$145.45	$145.45	$145.50
Purchase #5	$145.55	3.323%	$150.3866	$150.39	$150.40	$150.40
Purchase #6	$146.42	8.802%	$159.3079	$159.31	$159.30	$159.30
Purchase #7	$131.50	8.746%	$143.001	$143.00	$143.00	$143.00
7 purchase totals =	$902.38		$954.5289	$954.52	$954.50	$954.60