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	$123.41	3.548%	$127.7886	$127.79	$127.80	$127.80
Purchase #2	$30.57	11.322%	$34.0311	$34.03	$34.05	$34.00
Purchase #3	$153.62	11.752%	$171.6734	$171.67	$171.65	$171.70
Purchase #4	$40.77	7.768%	$43.937	$43.94	$43.95	$43.90
Purchase #5	$225.69	13.411%	$255.9573	$255.96	$255.95	$256.00
Purchase #6	$95.32	5.831%	$100.8781	$100.88	$100.90	$100.90
Purchase #7	$190.35	8.680%	$206.8724	$206.87	$206.85	$206.90
7 purchase totals =	$859.73		$941.1379	$941.14	$941.15	$941.20