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	$198.95	9.328%	$217.5081	$217.51	$217.50	$217.50
Purchase #2	$64.26	13.452%	$72.9043	$72.90	$72.90	$72.90
Purchase #3	$84.87	5.619%	$89.6388	$89.64	$89.65	$89.60
Purchase #4	$208.73	6.163%	$221.594	$221.59	$221.60	$221.60
Purchase #5	$176.35	13.327%	$199.8522	$199.85	$199.85	$199.90
Purchase #6	$179.26	8.684%	$194.8269	$194.83	$194.85	$194.80
Purchase #7	$6.38	3.370%	$6.595	$6.60	$6.60	$6.60
7 purchase totals =	$918.80		$1,002.9193	$1,002.92	$1,002.95	$1,002.90