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	$211.76	3.156%	$218.4431	$218.44	$218.45	$218.40
Purchase #2	$124.79	9.795%	$137.0132	$137.01	$137.00	$137.00
Purchase #3	$68.88	13.496%	$78.176	$78.18	$78.20	$78.20
Purchase #4	$92.38	10.208%	$101.8102	$101.81	$101.80	$101.80
Purchase #5	$241.89	13.400%	$274.3033	$274.30	$274.30	$274.30
Purchase #6	$87.70	13.828%	$99.8272	$99.83	$99.85	$99.80
Purchase #7	$245.31	10.819%	$271.8501	$271.85	$271.85	$271.90
7 purchase totals =	$1,072.71		$1,181.4231	$1,181.42	$1,181.45	$1,181.40