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	$44.29	4.240%	$46.1679	$46.17	$46.15	$46.20
Purchase #2	$35.57	13.735%	$40.4555	$40.46	$40.45	$40.50
Purchase #3	$176.89	6.218%	$187.889	$187.89	$187.90	$187.90
Purchase #4	$110.81	8.164%	$119.8565	$119.86	$119.85	$119.90
Purchase #5	$54.65	4.375%	$57.0409	$57.04	$57.05	$57.00
Purchase #6	$163.28	6.178%	$173.3674	$173.37	$173.35	$173.40
Purchase #7	$120.68	3.512%	$124.9183	$124.92	$124.90	$124.90
7 purchase totals =	$706.17		$749.6955	$749.71	$749.65	$749.80