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	$98.54	3.436%	$101.9258	$101.93	$101.95	$101.90
Purchase #2	$67.92	6.684%	$72.4598	$72.46	$72.45	$72.50
Purchase #3	$186.94	5.374%	$196.9862	$196.99	$197.00	$197.00
Purchase #4	$246.27	6.144%	$261.4008	$261.40	$261.40	$261.40
Purchase #5	$51.50	7.141%	$55.1776	$55.18	$55.20	$55.20
Purchase #6	$159.60	11.665%	$178.2173	$178.22	$178.20	$178.20
Purchase #7	$244.50	12.667%	$275.4708	$275.47	$275.45	$275.50
7 purchase totals =	$1,055.27		$1,141.6383	$1,141.65	$1,141.65	$1,141.70