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	$157.26	6.564%	$167.5825	$167.58	$167.60	$167.60
Purchase #2	$40.59	3.475%	$42.0005	$42.00	$42.00	$42.00
Purchase #3	$190.78	6.500%	$203.1807	$203.18	$203.20	$203.20
Purchase #4	$114.94	13.870%	$130.8822	$130.88	$130.90	$130.90
Purchase #5	$10.83	7.348%	$11.6258	$11.63	$11.65	$11.60
Purchase #6	$168.58	4.310%	$175.8458	$175.85	$175.85	$175.80
Purchase #7	$39.33	11.629%	$43.9037	$43.90	$43.90	$43.90
7 purchase totals =	$722.31		$775.0212	$775.02	$775.10	$775.00