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	$127.29	7.140%	$136.3785	$136.38	$136.40	$136.40
Purchase #2	$94.84	3.434%	$98.0968	$98.10	$98.10	$98.10
Purchase #3	$113.27	12.614%	$127.5579	$127.56	$127.55	$127.60
Purchase #4	$231.32	5.841%	$244.8314	$244.83	$244.85	$244.80
Purchase #5	$177.53	10.702%	$196.5293	$196.53	$196.55	$196.50
Purchase #6	$104.46	8.792%	$113.6441	$113.64	$113.65	$113.60
Purchase #7	$22.75	5.401%	$23.9787	$23.98	$24.00	$24.00
7 purchase totals =	$871.46		$941.0167	$941.02	$941.10	$941.00