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	$45.72	8.434%	$49.576	$49.58	$49.60	$49.60
Purchase #2	$85.80	13.615%	$97.4817	$97.48	$97.50	$97.50
Purchase #3	$216.59	12.460%	$243.5771	$243.58	$243.60	$243.60
Purchase #4	$53.41	10.518%	$59.0277	$59.03	$59.05	$59.00
Purchase #5	$195.67	6.641%	$208.6644	$208.66	$208.65	$208.70
Purchase #6	$32.39	4.500%	$33.8476	$33.85	$33.85	$33.80
Purchase #7	$134.60	7.351%	$144.4944	$144.49	$144.50	$144.50
7 purchase totals =	$764.18		$836.6689	$836.67	$836.75	$836.70