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	$171.25	6.612%	$182.5731	$182.57	$182.55	$182.60
Purchase #2	$80.64	12.715%	$90.8934	$90.89	$90.90	$90.90
Purchase #3	$124.90	13.193%	$141.3781	$141.38	$141.40	$141.40
Purchase #4	$173.44	7.422%	$186.3127	$186.31	$186.30	$186.30
Purchase #5	$185.45	10.182%	$204.3325	$204.33	$204.35	$204.30
Purchase #6	$81.45	8.283%	$88.1965	$88.20	$88.20	$88.20
Purchase #7	$34.41	10.545%	$38.0385	$38.04	$38.05	$38.00
7 purchase totals =	$851.54		$931.7248	$931.72	$931.75	$931.70