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	$204.39	12.670%	$230.2862	$230.29	$230.30	$230.30
Purchase #2	$234.48	11.214%	$260.7746	$260.77	$260.75	$260.80
Purchase #3	$140.75	10.746%	$155.875	$155.88	$155.90	$155.90
Purchase #4	$37.87	3.539%	$39.2102	$39.21	$39.20	$39.20
Purchase #5	$110.94	11.720%	$123.9422	$123.94	$123.95	$123.90
Purchase #6	$166.41	12.595%	$187.3693	$187.37	$187.35	$187.40
Purchase #7	$56.34	4.756%	$59.0195	$59.02	$59.00	$59.00
7 purchase totals =	$951.18		$1,056.4770	$1,056.48	$1,056.45	$1,056.50