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	$131.83	7.339%	$141.505	$141.51	$141.50	$141.50
Purchase #2	$214.47	11.337%	$238.7845	$238.78	$238.80	$238.80
Purchase #3	$19.45	11.433%	$21.6737	$21.67	$21.65	$21.70
Purchase #4	$183.97	3.526%	$190.4568	$190.46	$190.45	$190.50
Purchase #5	$66.50	8.596%	$72.2163	$72.22	$72.20	$72.20
Purchase #6	$34.98	3.306%	$36.1364	$36.14	$36.15	$36.10
Purchase #7	$242.90	13.827%	$276.4858	$276.49	$276.50	$276.50
7 purchase totals =	$894.10		$977.2585	$977.27	$977.25	$977.30