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	$161.63	6.592%	$172.2846	$172.28	$172.30	$172.30
Purchase #2	$62.38	7.264%	$66.9113	$66.91	$66.90	$66.90
Purchase #3	$231.72	13.454%	$262.8956	$262.90	$262.90	$262.90
Purchase #4	$34.70	3.205%	$35.8121	$35.81	$35.80	$35.80
Purchase #5	$78.88	12.159%	$88.471	$88.47	$88.45	$88.50
Purchase #6	$148.60	13.657%	$168.8943	$168.89	$168.90	$168.90
Purchase #7	$219.54	8.828%	$238.921	$238.92	$238.90	$238.90
7 purchase totals =	$937.45		$1,034.1899	$1,034.18	$1,034.15	$1,034.20