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	$169.78	7.252%	$182.0924	$182.09	$182.10	$182.10
Purchase #2	$121.87	5.213%	$128.2231	$128.22	$128.20	$128.20
Purchase #3	$161.90	4.146%	$168.6124	$168.61	$168.60	$168.60
Purchase #4	$23.51	10.229%	$25.9148	$25.91	$25.90	$25.90
Purchase #5	$176.72	7.103%	$189.2724	$189.27	$189.25	$189.30
Purchase #6	$145.70	3.480%	$150.7704	$150.77	$150.75	$150.80
Purchase #7	$169.89	12.699%	$191.4643	$191.46	$191.45	$191.50
7 purchase totals =	$969.37		$1,036.3498	$1,036.33	$1,036.25	$1,036.40