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	$100.91	10.708%	$111.7154	$111.72	$111.70	$111.70
Purchase #2	$180.65	3.721%	$187.372	$187.37	$187.35	$187.40
Purchase #3	$214.31	13.782%	$243.8462	$243.85	$243.85	$243.80
Purchase #4	$137.74	5.189%	$144.8873	$144.89	$144.90	$144.90
Purchase #5	$118.38	3.726%	$122.7908	$122.79	$122.80	$122.80
Purchase #6	$72.58	13.480%	$82.3638	$82.36	$82.35	$82.40
Purchase #7	$229.27	11.688%	$256.0671	$256.07	$256.05	$256.10
7 purchase totals =	$1,053.84		$1,149.0426	$1,149.05	$1,149.00	$1,149.10