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	$41.47	10.342%	$45.7588	$45.76	$45.75	$45.80
Purchase #2	$111.79	6.483%	$119.0373	$119.04	$119.05	$119.00
Purchase #3	$212.61	3.327%	$219.6835	$219.68	$219.70	$219.70
Purchase #4	$246.42	11.431%	$274.5883	$274.59	$274.60	$274.60
Purchase #5	$130.53	13.204%	$147.7652	$147.77	$147.75	$147.80
Purchase #6	$84.46	13.188%	$95.5986	$95.60	$95.60	$95.60
Purchase #7	$33.70	11.773%	$37.6675	$37.67	$37.65	$37.70
7 purchase totals =	$860.98		$940.0992	$940.11	$940.10	$940.20