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	$149.92	10.823%	$166.1458	$166.15	$166.15	$166.10
Purchase #2	$21.61	11.680%	$24.134	$24.13	$24.15	$24.10
Purchase #3	$219.94	11.454%	$245.1319	$245.13	$245.15	$245.10
Purchase #4	$212.89	8.870%	$231.7733	$231.77	$231.75	$231.80
Purchase #5	$192.37	3.694%	$199.4761	$199.48	$199.50	$199.50
Purchase #6	$123.49	3.141%	$127.3688	$127.37	$127.35	$127.40
Purchase #7	$38.70	3.598%	$40.0924	$40.09	$40.10	$40.10
7 purchase totals =	$958.92		$1,034.1223	$1,034.12	$1,034.15	$1,034.10