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	$182.38	9.323%	$199.3833	$199.38	$199.40	$199.40
Purchase #2	$14.59	8.828%	$15.878	$15.88	$15.90	$15.90
Purchase #3	$99.90	11.547%	$111.4355	$111.44	$111.45	$111.40
Purchase #4	$113.50	7.822%	$122.378	$122.38	$122.40	$122.40
Purchase #5	$145.30	10.336%	$160.3182	$160.32	$160.30	$160.30
Purchase #6	$10.59	8.298%	$11.4688	$11.47	$11.45	$11.50
Purchase #7	$36.49	3.222%	$37.6657	$37.67	$37.65	$37.70
7 purchase totals =	$602.75		$658.5275	$658.54	$658.55	$658.60