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	$113.89	10.135%	$125.4328	$125.43	$125.45	$125.40
Purchase #2	$157.61	10.248%	$173.7619	$173.76	$173.75	$173.80
Purchase #3	$164.90	10.673%	$182.4998	$182.50	$182.50	$182.50
Purchase #4	$78.36	13.437%	$88.8892	$88.89	$88.90	$88.90
Purchase #5	$139.78	9.312%	$152.7963	$152.80	$152.80	$152.80
Purchase #6	$65.89	11.481%	$73.4548	$73.45	$73.45	$73.50
Purchase #7	$7.59	5.167%	$7.9822	$7.98	$8.00	$8.00
7 purchase totals =	$728.02		$804.8170	$804.81	$804.85	$804.90