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	$234.66	3.338%	$242.493	$242.49	$242.50	$242.50
Purchase #2	$63.77	13.584%	$72.4325	$72.43	$72.45	$72.40
Purchase #3	$149.48	10.312%	$164.8944	$164.89	$164.90	$164.90
Purchase #4	$100.37	12.648%	$113.0648	$113.06	$113.05	$113.10
Purchase #5	$104.44	7.186%	$111.9451	$111.95	$111.95	$111.90
Purchase #6	$240.26	13.653%	$273.0627	$273.06	$273.05	$273.10
Purchase #7	$196.75	9.867%	$216.1633	$216.16	$216.15	$216.20
7 purchase totals =	$1,089.73		$1,194.0558	$1,194.04	$1,194.05	$1,194.10