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	$207.90	3.420%	$215.0102	$215.01	$215.00	$215.00
Purchase #2	$132.82	13.337%	$150.5342	$150.53	$150.55	$150.50
Purchase #3	$38.95	11.794%	$43.5438	$43.54	$43.55	$43.50
Purchase #4	$167.60	12.117%	$187.9081	$187.91	$187.90	$187.90
Purchase #5	$190.56	8.122%	$206.0373	$206.04	$206.05	$206.00
Purchase #6	$75.46	10.528%	$83.4044	$83.40	$83.40	$83.40
Purchase #7	$153.87	4.211%	$160.3495	$160.35	$160.35	$160.30
7 purchase totals =	$967.16		$1,046.7875	$1,046.78	$1,046.80	$1,046.60