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	$199.34	4.481%	$208.2724	$208.27	$208.25	$208.30
Purchase #2	$40.58	8.315%	$43.9542	$43.95	$43.95	$44.00
Purchase #3	$197.64	12.268%	$221.8865	$221.89	$221.90	$221.90
Purchase #4	$41.39	4.773%	$43.3655	$43.37	$43.35	$43.40
Purchase #5	$41.56	12.192%	$46.627	$46.63	$46.65	$46.60
Purchase #6	$68.44	4.360%	$71.424	$71.42	$71.40	$71.40
Purchase #7	$13.62	6.533%	$14.5098	$14.51	$14.50	$14.50
7 purchase totals =	$602.57		$650.0394	$650.04	$650.00	$650.10