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	$126.60	5.342%	$133.363	$133.36	$133.35	$133.40
Purchase #2	$33.51	13.131%	$37.9102	$37.91	$37.90	$37.90
Purchase #3	$134.85	13.853%	$153.5308	$153.53	$153.55	$153.50
Purchase #4	$46.81	4.757%	$49.0368	$49.04	$49.05	$49.00
Purchase #5	$90.66	11.284%	$100.8901	$100.89	$100.90	$100.90
Purchase #6	$198.46	7.359%	$213.0647	$213.06	$213.05	$213.10
Purchase #7	$54.25	8.601%	$58.916	$58.92	$58.90	$58.90
7 purchase totals =	$685.14		$746.7116	$746.71	$746.70	$746.70