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	$32.30	4.790%	$33.8472	$33.85	$33.85	$33.80
Purchase #2	$140.73	8.628%	$152.8722	$152.87	$152.85	$152.90
Purchase #3	$185.34	12.447%	$208.4093	$208.41	$208.40	$208.40
Purchase #4	$109.99	4.359%	$114.7845	$114.78	$114.80	$114.80
Purchase #5	$51.93	3.871%	$53.9402	$53.94	$53.95	$53.90
Purchase #6	$31.64	8.735%	$34.4038	$34.40	$34.40	$34.40
Purchase #7	$168.56	13.548%	$191.3965	$191.40	$191.40	$191.40
7 purchase totals =	$720.49		$789.6537	$789.65	$789.65	$789.60