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	$10.86	7.380%	$11.6615	$11.66	$11.65	$11.70
Purchase #2	$33.48	11.759%	$37.4169	$37.42	$37.40	$37.40
Purchase #3	$133.45	4.488%	$139.4392	$139.44	$139.45	$139.40
Purchase #4	$205.29	8.506%	$222.752	$222.75	$222.75	$222.80
Purchase #5	$76.69	3.780%	$79.5889	$79.59	$79.60	$79.60
Purchase #6	$164.34	9.723%	$180.3188	$180.32	$180.30	$180.30
Purchase #7	$214.27	13.549%	$243.3014	$243.30	$243.30	$243.30
7 purchase totals =	$838.38		$914.4787	$914.48	$914.45	$914.50