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	$173.28	13.591%	$196.8305	$196.83	$196.85	$196.80
Purchase #2	$48.56	9.515%	$53.1805	$53.18	$53.20	$53.20
Purchase #3	$24.33	13.707%	$27.6649	$27.66	$27.65	$27.70
Purchase #4	$72.59	8.728%	$78.9257	$78.93	$78.95	$78.90
Purchase #5	$88.87	9.348%	$97.1776	$97.18	$97.20	$97.20
Purchase #6	$230.90	13.169%	$261.3072	$261.31	$261.30	$261.30
Purchase #7	$145.44	5.701%	$153.7315	$153.73	$153.75	$153.70
7 purchase totals =	$783.97		$868.8179	$868.82	$868.90	$868.80