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	$237.94	8.699%	$258.6384	$258.64	$258.65	$258.60
Purchase #2	$217.67	9.549%	$238.4553	$238.46	$238.45	$238.50
Purchase #3	$34.88	8.589%	$37.8758	$37.88	$37.90	$37.90
Purchase #4	$89.99	13.520%	$102.1566	$102.16	$102.15	$102.20
Purchase #5	$78.86	4.755%	$82.6098	$82.61	$82.60	$82.60
Purchase #6	$31.65	4.794%	$33.1673	$33.17	$33.15	$33.20
Purchase #7	$56.93	4.786%	$59.6547	$59.65	$59.65	$59.70
7 purchase totals =	$747.92		$812.5579	$812.57	$812.55	$812.70