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	$229.54	5.190%	$241.4531	$241.45	$241.45	$241.50
Purchase #2	$178.28	10.266%	$196.5822	$196.58	$196.60	$196.60
Purchase #3	$148.52	10.775%	$164.523	$164.52	$164.50	$164.50
Purchase #4	$85.83	9.574%	$94.0474	$94.05	$94.05	$94.00
Purchase #5	$241.66	3.821%	$250.8938	$250.89	$250.90	$250.90
Purchase #6	$129.61	13.264%	$146.8015	$146.80	$146.80	$146.80
Purchase #7	$117.34	12.345%	$131.8256	$131.83	$131.85	$131.80
7 purchase totals =	$1,130.78		$1,226.1266	$1,226.12	$1,226.15	$1,226.10