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	$97.41	4.487%	$101.7808	$101.78	$101.80	$101.80
Purchase #2	$195.71	11.645%	$218.5004	$218.50	$218.50	$218.50
Purchase #3	$214.87	10.664%	$237.7837	$237.78	$237.80	$237.80
Purchase #4	$48.40	11.205%	$53.8232	$53.82	$53.80	$53.80
Purchase #5	$33.62	9.324%	$36.7547	$36.75	$36.75	$36.80
Purchase #6	$162.34	6.134%	$172.2979	$172.30	$172.30	$172.30
Purchase #7	$67.32	6.191%	$71.4878	$71.49	$71.50	$71.50
7 purchase totals =	$819.67		$892.4285	$892.42	$892.45	$892.50