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	$160.51	5.742%	$169.7265	$169.73	$169.75	$169.70
Purchase #2	$159.75	9.139%	$174.3496	$174.35	$174.35	$174.30
Purchase #3	$52.57	6.284%	$55.8735	$55.87	$55.85	$55.90
Purchase #4	$132.41	13.563%	$150.3688	$150.37	$150.35	$150.40
Purchase #5	$175.43	8.361%	$190.0977	$190.10	$190.10	$190.10
Purchase #6	$157.98	11.475%	$176.1082	$176.11	$176.10	$176.10
Purchase #7	$56.85	4.752%	$59.5515	$59.55	$59.55	$59.60
7 purchase totals =	$895.50		$976.0758	$976.08	$976.05	$976.10