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	$35.76	3.509%	$37.0148	$37.01	$37.00	$37.00
Purchase #2	$84.47	6.161%	$89.6742	$89.67	$89.65	$89.70
Purchase #3	$53.68	6.775%	$57.3168	$57.32	$57.30	$57.30
Purchase #4	$216.74	11.412%	$241.4744	$241.47	$241.45	$241.50
Purchase #5	$101.42	10.576%	$112.1462	$112.15	$112.15	$112.10
Purchase #6	$53.61	5.790%	$56.714	$56.71	$56.70	$56.70
Purchase #7	$104.88	10.467%	$115.8578	$115.86	$115.85	$115.90
7 purchase totals =	$650.56		$710.1982	$710.19	$710.10	$710.20