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	$172.63	11.562%	$192.5895	$192.59	$192.60	$192.60
Purchase #2	$82.58	11.474%	$92.0552	$92.06	$92.05	$92.10
Purchase #3	$95.77	12.632%	$107.8677	$107.87	$107.85	$107.90
Purchase #4	$194.51	11.313%	$216.5149	$216.51	$216.50	$216.50
Purchase #5	$42.57	12.800%	$48.019	$48.02	$48.00	$48.00
Purchase #6	$28.48	13.872%	$32.4307	$32.43	$32.45	$32.40
Purchase #7	$123.47	7.853%	$133.1661	$133.17	$133.15	$133.20
7 purchase totals =	$740.01		$822.6431	$822.65	$822.60	$822.70