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	$216.44	3.452%	$223.9115	$223.91	$223.90	$223.90
Purchase #2	$65.25	11.352%	$72.6572	$72.66	$72.65	$72.70
Purchase #3	$149.60	13.569%	$169.8992	$169.90	$169.90	$169.90
Purchase #4	$186.91	13.118%	$211.4289	$211.43	$211.45	$211.40
Purchase #5	$49.88	5.429%	$52.588	$52.59	$52.60	$52.60
Purchase #6	$225.97	6.178%	$239.9304	$239.93	$239.95	$239.90
Purchase #7	$34.59	3.627%	$35.8446	$35.84	$35.85	$35.80
7 purchase totals =	$928.64		$1,006.2598	$1,006.26	$1,006.30	$1,006.20