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	$123.38	7.645%	$132.8124	$132.81	$132.80	$132.80
Purchase #2	$133.26	10.684%	$147.4975	$147.50	$147.50	$147.50
Purchase #3	$200.53	13.514%	$227.6296	$227.63	$227.65	$227.60
Purchase #4	$25.80	10.659%	$28.55	$28.55	$28.55	$28.60
Purchase #5	$32.72	9.393%	$35.7934	$35.79	$35.80	$35.80
Purchase #6	$140.51	7.282%	$150.7419	$150.74	$150.75	$150.70
Purchase #7	$95.41	4.694%	$99.8885	$99.89	$99.90	$99.90
7 purchase totals =	$751.61		$822.9133	$822.91	$822.95	$822.90