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	$96.71	4.733%	$101.2873	$101.29	$101.30	$101.30
Purchase #2	$200.57	13.417%	$227.4805	$227.48	$227.50	$227.50
Purchase #3	$38.26	4.174%	$39.857	$39.86	$39.85	$39.90
Purchase #4	$55.76	6.330%	$59.2896	$59.29	$59.30	$59.30
Purchase #5	$240.85	6.473%	$256.4402	$256.44	$256.45	$256.40
Purchase #6	$187.89	7.644%	$202.2523	$202.25	$202.25	$202.30
Purchase #7	$241.54	13.870%	$275.0416	$275.04	$275.05	$275.00
7 purchase totals =	$1,061.58		$1,161.6485	$1,161.65	$1,161.70	$1,161.70