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	$120.26	13.502%	$136.4975	$136.50	$136.50	$136.50
Purchase #2	$237.26	10.208%	$261.4795	$261.48	$261.50	$261.50
Purchase #3	$208.36	9.714%	$228.6001	$228.60	$228.60	$228.60
Purchase #4	$78.69	5.292%	$82.8543	$82.85	$82.85	$82.90
Purchase #5	$32.32	11.838%	$36.146	$36.15	$36.15	$36.10
Purchase #6	$57.87	9.128%	$63.1524	$63.15	$63.15	$63.20
Purchase #7	$93.57	7.502%	$100.5896	$100.59	$100.60	$100.60
7 purchase totals =	$828.33		$909.3194	$909.32	$909.35	$909.40