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	$230.32	5.314%	$242.5592	$242.56	$242.55	$242.60
Purchase #2	$30.42	3.868%	$31.5966	$31.60	$31.60	$31.60
Purchase #3	$161.46	6.858%	$172.5329	$172.53	$172.55	$172.50
Purchase #4	$101.68	11.768%	$113.6457	$113.65	$113.65	$113.60
Purchase #5	$85.61	9.282%	$93.5563	$93.56	$93.55	$93.60
Purchase #6	$34.70	3.460%	$35.9006	$35.90	$35.90	$35.90
Purchase #7	$28.79	12.712%	$32.4498	$32.45	$32.45	$32.40
7 purchase totals =	$672.98		$722.2411	$722.25	$722.25	$722.20