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	$205.78	11.364%	$229.1648	$229.16	$229.15	$229.20
Purchase #2	$155.34	12.567%	$174.8616	$174.86	$174.85	$174.90
Purchase #3	$116.57	3.672%	$120.8505	$120.85	$120.85	$120.90
Purchase #4	$157.49	11.652%	$175.8407	$175.84	$175.85	$175.80
Purchase #5	$228.95	5.531%	$241.6132	$241.61	$241.60	$241.60
Purchase #6	$79.72	6.624%	$85.0007	$85.00	$85.00	$85.00
Purchase #7	$71.59	9.554%	$78.4297	$78.43	$78.45	$78.40
7 purchase totals =	$1,015.44		$1,105.7612	$1,105.75	$1,105.75	$1,105.80