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	$34.87	7.694%	$37.5529	$37.55	$37.55	$37.60
Purchase #2	$84.34	9.713%	$92.5319	$92.53	$92.55	$92.50
Purchase #3	$137.64	4.679%	$144.0802	$144.08	$144.10	$144.10
Purchase #4	$204.77	11.591%	$228.5049	$228.50	$228.50	$228.50
Purchase #5	$224.41	7.541%	$241.3328	$241.33	$241.35	$241.30
Purchase #6	$164.97	8.121%	$178.3672	$178.37	$178.35	$178.40
Purchase #7	$9.83	3.160%	$10.1406	$10.14	$10.15	$10.10
7 purchase totals =	$860.83		$932.5105	$932.50	$932.55	$932.50