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	$157.52	11.198%	$175.1591	$175.16	$175.15	$175.20
Purchase #2	$35.47	13.729%	$40.3397	$40.34	$40.35	$40.30
Purchase #3	$90.84	9.860%	$99.7968	$99.80	$99.80	$99.80
Purchase #4	$37.67	6.541%	$40.134	$40.13	$40.15	$40.10
Purchase #5	$240.60	8.855%	$261.9051	$261.91	$261.90	$261.90
Purchase #6	$216.55	3.598%	$224.3415	$224.34	$224.35	$224.30
Purchase #7	$39.90	8.322%	$43.2205	$43.22	$43.20	$43.20
7 purchase totals =	$818.55		$884.8967	$884.90	$884.90	$884.80