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	$159.78	8.478%	$173.3261	$173.33	$173.35	$173.30
Purchase #2	$33.61	13.841%	$38.262	$38.26	$38.25	$38.30
Purchase #3	$38.36	11.603%	$42.8109	$42.81	$42.80	$42.80
Purchase #4	$48.69	3.716%	$50.4993	$50.50	$50.50	$50.50
Purchase #5	$31.87	8.334%	$34.526	$34.53	$34.55	$34.50
Purchase #6	$38.95	9.472%	$42.6393	$42.64	$42.65	$42.60
Purchase #7	$182.31	9.759%	$200.1016	$200.10	$200.10	$200.10
7 purchase totals =	$533.57		$582.1652	$582.17	$582.20	$582.10