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	$132.48	13.377%	$150.2018	$150.20	$150.20	$150.20
Purchase #2	$92.60	8.219%	$100.2108	$100.21	$100.20	$100.20
Purchase #3	$216.90	13.787%	$246.804	$246.80	$246.80	$246.80
Purchase #4	$79.34	3.521%	$82.1336	$82.13	$82.15	$82.10
Purchase #5	$87.71	13.850%	$99.8578	$99.86	$99.85	$99.90
Purchase #6	$104.43	11.311%	$116.2421	$116.24	$116.25	$116.20
Purchase #7	$157.73	6.649%	$168.2175	$168.22	$168.20	$168.20
7 purchase totals =	$871.19		$963.6676	$963.66	$963.65	$963.60