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	$147.70	13.709%	$167.9482	$167.95	$167.95	$167.90
Purchase #2	$32.92	7.739%	$35.4677	$35.47	$35.45	$35.50
Purchase #3	$74.50	9.531%	$81.6006	$81.60	$81.60	$81.60
Purchase #4	$154.86	4.328%	$161.5623	$161.56	$161.55	$161.60
Purchase #5	$72.83	7.121%	$78.0162	$78.02	$78.00	$78.00
Purchase #6	$53.87	8.861%	$58.6434	$58.64	$58.65	$58.60
Purchase #7	$233.89	3.557%	$242.2095	$242.21	$242.20	$242.20
7 purchase totals =	$770.57		$825.4479	$825.45	$825.40	$825.40