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	$124.39	6.576%	$132.5699	$132.57	$132.55	$132.60
Purchase #2	$43.85	3.758%	$45.4979	$45.50	$45.50	$45.50
Purchase #3	$232.85	7.409%	$250.1019	$250.10	$250.10	$250.10
Purchase #4	$77.25	6.447%	$82.2303	$82.23	$82.25	$82.20
Purchase #5	$202.92	6.547%	$216.2052	$216.21	$216.20	$216.20
Purchase #6	$38.33	13.718%	$43.5881	$43.59	$43.60	$43.60
Purchase #7	$144.63	9.203%	$157.9403	$157.94	$157.95	$157.90
7 purchase totals =	$864.22		$928.1336	$928.14	$928.15	$928.10