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	$159.64	3.329%	$164.9544	$164.95	$164.95	$165.00
Purchase #2	$247.25	3.761%	$256.5491	$256.55	$256.55	$256.50
Purchase #3	$40.39	4.863%	$42.3542	$42.35	$42.35	$42.40
Purchase #4	$72.77	10.289%	$80.2573	$80.26	$80.25	$80.30
Purchase #5	$21.66	3.804%	$22.4839	$22.48	$22.50	$22.50
Purchase #6	$250.74	12.118%	$281.1247	$281.12	$281.10	$281.10
Purchase #7	$92.56	3.532%	$95.8292	$95.83	$95.85	$95.80
7 purchase totals =	$885.01		$943.5528	$943.54	$943.55	$943.60