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	$126.86	8.516%	$137.6634	$137.66	$137.65	$137.70
Purchase #2	$122.64	3.351%	$126.7497	$126.75	$126.75	$126.70
Purchase #3	$83.54	7.581%	$89.8732	$89.87	$89.85	$89.90
Purchase #4	$197.54	4.242%	$205.9196	$205.92	$205.90	$205.90
Purchase #5	$39.59	12.176%	$44.4105	$44.41	$44.40	$44.40
Purchase #6	$248.67	12.251%	$279.1346	$279.13	$279.15	$279.10
Purchase #7	$204.66	5.865%	$216.6633	$216.66	$216.65	$216.70
7 purchase totals =	$1,023.50		$1,100.4143	$1,100.40	$1,100.35	$1,100.40