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	$34.66	3.340%	$35.8176	$35.82	$35.80	$35.80
Purchase #2	$152.77	10.575%	$168.9254	$168.93	$168.95	$168.90
Purchase #3	$139.58	8.610%	$151.5978	$151.60	$151.60	$151.60
Purchase #4	$204.86	7.237%	$219.6857	$219.69	$219.70	$219.70
Purchase #5	$133.75	8.206%	$144.7255	$144.73	$144.75	$144.70
Purchase #6	$226.46	11.198%	$251.819	$251.82	$251.80	$251.80
Purchase #7	$155.78	10.212%	$171.6883	$171.69	$171.70	$171.70
7 purchase totals =	$1,047.86		$1,144.2593	$1,144.28	$1,144.30	$1,144.20