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	$56.39	6.132%	$59.8478	$59.85	$59.85	$59.80
Purchase #2	$98.90	13.736%	$112.4849	$112.48	$112.50	$112.50
Purchase #3	$126.51	11.571%	$141.1485	$141.15	$141.15	$141.10
Purchase #4	$151.34	12.395%	$170.0986	$170.10	$170.10	$170.10
Purchase #5	$150.45	3.302%	$155.4179	$155.42	$155.40	$155.40
Purchase #6	$184.87	5.672%	$195.3558	$195.36	$195.35	$195.40
Purchase #7	$100.33	12.274%	$112.6445	$112.64	$112.65	$112.60
7 purchase totals =	$868.79		$946.9980	$947.00	$947.00	$946.90