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	$31.39	5.554%	$33.1334	$33.13	$33.15	$33.10
Purchase #2	$59.55	11.780%	$66.565	$66.57	$66.55	$66.60
Purchase #3	$140.84	12.297%	$158.1591	$158.16	$158.15	$158.20
Purchase #4	$181.65	13.308%	$205.824	$205.82	$205.80	$205.80
Purchase #5	$42.41	3.275%	$43.7989	$43.80	$43.80	$43.80
Purchase #6	$227.82	5.843%	$241.1315	$241.13	$241.15	$241.10
Purchase #7	$128.84	3.543%	$133.4048	$133.40	$133.40	$133.40
7 purchase totals =	$812.50		$882.0167	$882.01	$882.00	$882.00