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	$132.94	8.804%	$144.644	$144.64	$144.65	$144.60
Purchase #2	$87.35	10.437%	$96.4667	$96.47	$96.45	$96.50
Purchase #3	$82.81	8.697%	$90.012	$90.01	$90.00	$90.00
Purchase #4	$64.57	12.334%	$72.5341	$72.53	$72.55	$72.50
Purchase #5	$56.37	4.480%	$58.8954	$58.90	$58.90	$58.90
Purchase #6	$83.77	12.659%	$94.3744	$94.37	$94.35	$94.40
Purchase #7	$35.98	4.616%	$37.6408	$37.64	$37.65	$37.60
7 purchase totals =	$543.79		$594.5674	$594.56	$594.55	$594.50