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	$164.35	12.313%	$184.5864	$184.59	$184.60	$184.60
Purchase #2	$35.61	4.459%	$37.1978	$37.20	$37.20	$37.20
Purchase #3	$214.38	11.567%	$239.1773	$239.18	$239.20	$239.20
Purchase #4	$17.31	6.632%	$18.458	$18.46	$18.45	$18.50
Purchase #5	$197.83	12.352%	$222.266	$222.27	$222.25	$222.30
Purchase #6	$36.50	12.105%	$40.9183	$40.92	$40.90	$40.90
Purchase #7	$159.30	6.106%	$169.0269	$169.03	$169.05	$169.00
7 purchase totals =	$825.28		$911.6307	$911.65	$911.65	$911.70