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	$168.37	7.625%	$181.2082	$181.21	$181.20	$181.20
Purchase #2	$105.45	3.273%	$108.9014	$108.90	$108.90	$108.90
Purchase #3	$208.56	9.150%	$227.6432	$227.64	$227.65	$227.60
Purchase #4	$187.30	5.523%	$197.6446	$197.64	$197.65	$197.60
Purchase #5	$131.72	10.275%	$145.2542	$145.25	$145.25	$145.30
Purchase #6	$40.38	12.153%	$45.2874	$45.29	$45.30	$45.30
Purchase #7	$29.90	12.485%	$33.633	$33.63	$33.65	$33.60
7 purchase totals =	$871.68		$939.5720	$939.56	$939.60	$939.50