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	$95.93	9.575%	$105.1153	$105.12	$105.10	$105.10
Purchase #2	$174.82	9.747%	$191.8597	$191.86	$191.85	$191.90
Purchase #3	$159.42	5.552%	$168.271	$168.27	$168.25	$168.30
Purchase #4	$11.34	11.741%	$12.6714	$12.67	$12.65	$12.70
Purchase #5	$31.32	13.709%	$35.6137	$35.61	$35.60	$35.60
Purchase #6	$52.27	5.392%	$55.0884	$55.09	$55.10	$55.10
Purchase #7	$131.80	12.824%	$148.702	$148.70	$148.70	$148.70
7 purchase totals =	$656.90		$717.3215	$717.32	$717.25	$717.40