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	$195.50	6.874%	$208.9387	$208.94	$208.95	$208.90
Purchase #2	$81.51	11.238%	$90.6701	$90.67	$90.65	$90.70
Purchase #3	$99.49	6.361%	$105.8186	$105.82	$105.80	$105.80
Purchase #4	$41.42	8.227%	$44.8276	$44.83	$44.85	$44.80
Purchase #5	$67.33	7.327%	$72.2633	$72.26	$72.25	$72.30
Purchase #6	$42.66	13.298%	$48.3329	$48.33	$48.35	$48.30
Purchase #7	$212.41	9.323%	$232.213	$232.21	$232.20	$232.20
7 purchase totals =	$740.32		$803.0642	$803.06	$803.05	$803.00