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	$146.91	10.863%	$162.8688	$162.87	$162.85	$162.90
Purchase #2	$39.82	7.729%	$42.8977	$42.90	$42.90	$42.90
Purchase #3	$20.91	5.581%	$22.077	$22.08	$22.10	$22.10
Purchase #4	$239.89	13.176%	$271.4979	$271.50	$271.50	$271.50
Purchase #5	$142.51	5.442%	$150.2654	$150.27	$150.25	$150.30
Purchase #6	$214.69	5.726%	$226.9831	$226.98	$227.00	$227.00
Purchase #7	$175.93	12.167%	$197.3354	$197.34	$197.35	$197.30
7 purchase totals =	$980.66		$1,073.9253	$1,073.94	$1,073.95	$1,074.00