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	$11.39	5.732%	$12.0429	$12.04	$12.05	$12.00
Purchase #2	$37.87	13.440%	$42.9597	$42.96	$42.95	$43.00
Purchase #3	$35.50	5.108%	$37.3133	$37.31	$37.30	$37.30
Purchase #4	$32.68	11.297%	$36.3719	$36.37	$36.35	$36.40
Purchase #5	$107.86	9.841%	$118.4745	$118.47	$118.45	$118.50
Purchase #6	$133.91	5.440%	$141.1947	$141.19	$141.20	$141.20
Purchase #7	$70.51	13.609%	$80.1057	$80.11	$80.10	$80.10
7 purchase totals =	$429.72		$468.4627	$468.45	$468.40	$468.50