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	$168.33	8.565%	$182.7475	$182.75	$182.75	$182.70
Purchase #2	$171.38	7.635%	$184.4649	$184.46	$184.45	$184.50
Purchase #3	$151.93	5.431%	$160.1813	$160.18	$160.20	$160.20
Purchase #4	$57.60	9.189%	$62.8929	$62.89	$62.90	$62.90
Purchase #5	$221.32	5.102%	$232.6117	$232.61	$232.60	$232.60
Purchase #6	$160.55	4.646%	$168.0092	$168.01	$168.00	$168.00
Purchase #7	$191.64	4.612%	$200.4784	$200.48	$200.50	$200.50
7 purchase totals =	$1,122.75		$1,191.3859	$1,191.38	$1,191.40	$1,191.40