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	$73.43	12.774%	$82.8099	$82.81	$82.80	$82.80
Purchase #2	$82.79	10.587%	$91.555	$91.56	$91.55	$91.60
Purchase #3	$225.66	12.115%	$252.9987	$253.00	$253.00	$253.00
Purchase #4	$32.27	13.491%	$36.6235	$36.62	$36.60	$36.60
Purchase #5	$163.61	9.713%	$179.5014	$179.50	$179.50	$179.50
Purchase #6	$215.35	3.401%	$222.6741	$222.67	$222.65	$222.70
Purchase #7	$171.53	11.853%	$191.8615	$191.86	$191.85	$191.90
7 purchase totals =	$964.64		$1,058.0241	$1,058.02	$1,057.95	$1,058.10