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	$72.97	12.622%	$82.1803	$82.18	$82.20	$82.20
Purchase #2	$80.32	11.426%	$89.4974	$89.50	$89.50	$89.50
Purchase #3	$136.89	11.334%	$152.4051	$152.41	$152.40	$152.40
Purchase #4	$158.99	11.769%	$177.7015	$177.70	$177.70	$177.70
Purchase #5	$150.93	4.720%	$158.0539	$158.05	$158.05	$158.10
Purchase #6	$238.34	3.447%	$246.5556	$246.56	$246.55	$246.60
Purchase #7	$179.52	5.676%	$189.7096	$189.71	$189.70	$189.70
7 purchase totals =	$1,017.96		$1,096.1034	$1,096.11	$1,096.10	$1,096.20