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	$167.64	5.574%	$176.9843	$176.98	$177.00	$177.00
Purchase #2	$70.72	3.151%	$72.9484	$72.95	$72.95	$72.90
Purchase #3	$89.50	9.473%	$97.9783	$97.98	$98.00	$98.00
Purchase #4	$90.36	10.182%	$99.5605	$99.56	$99.55	$99.60
Purchase #5	$162.86	4.406%	$170.0356	$170.04	$170.05	$170.00
Purchase #6	$59.39	12.490%	$66.8078	$66.81	$66.80	$66.80
Purchase #7	$156.94	8.235%	$169.864	$169.86	$169.85	$169.90
7 purchase totals =	$797.41		$854.1789	$854.18	$854.20	$854.20