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	$230.48	8.534%	$250.1492	$250.15	$250.15	$250.10
Purchase #2	$14.51	7.448%	$15.5907	$15.59	$15.60	$15.60
Purchase #3	$187.36	13.840%	$213.2906	$213.29	$213.30	$213.30
Purchase #4	$50.67	4.150%	$52.7728	$52.77	$52.75	$52.80
Purchase #5	$30.33	7.501%	$32.6051	$32.61	$32.60	$32.60
Purchase #6	$132.95	13.439%	$150.8172	$150.82	$150.80	$150.80
Purchase #7	$29.91	8.709%	$32.5149	$32.51	$32.50	$32.50
7 purchase totals =	$676.21		$747.7405	$747.74	$747.70	$747.70