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	$99.26	13.286%	$112.4477	$112.45	$112.45	$112.40
Purchase #2	$202.89	6.726%	$216.5364	$216.54	$216.55	$216.50
Purchase #3	$34.54	4.797%	$36.1969	$36.20	$36.20	$36.20
Purchase #4	$132.83	13.269%	$150.4552	$150.46	$150.45	$150.50
Purchase #5	$243.28	12.798%	$274.415	$274.42	$274.40	$274.40
Purchase #6	$14.73	3.329%	$15.2204	$15.22	$15.20	$15.20
Purchase #7	$114.67	7.847%	$123.6682	$123.67	$123.65	$123.70
7 purchase totals =	$842.20		$928.9398	$928.96	$928.90	$928.90