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	$140.50	7.342%	$150.8155	$150.82	$150.80	$150.80
Purchase #2	$121.65	12.690%	$137.0874	$137.09	$137.10	$137.10
Purchase #3	$146.72	3.496%	$151.8493	$151.85	$151.85	$151.80
Purchase #4	$26.85	7.702%	$28.918	$28.92	$28.90	$28.90
Purchase #5	$240.35	6.717%	$256.4943	$256.49	$256.50	$256.50
Purchase #6	$104.59	9.738%	$114.775	$114.78	$114.80	$114.80
Purchase #7	$196.84	3.810%	$204.3396	$204.34	$204.35	$204.30
7 purchase totals =	$977.50		$1,044.2791	$1,044.29	$1,044.30	$1,044.20