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	$196.73	10.740%	$217.8588	$217.86	$217.85	$217.90
Purchase #2	$36.66	11.328%	$40.8128	$40.81	$40.80	$40.80
Purchase #3	$154.29	3.619%	$159.8738	$159.87	$159.85	$159.90
Purchase #4	$118.90	7.742%	$128.1052	$128.11	$128.10	$128.10
Purchase #5	$12.77	3.244%	$13.1843	$13.18	$13.20	$13.20
Purchase #6	$177.68	6.299%	$188.8721	$188.87	$188.85	$188.90
Purchase #7	$215.34	6.562%	$229.4706	$229.47	$229.45	$229.50
7 purchase totals =	$912.37		$978.1776	$978.17	$978.10	$978.30