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	$166.98	7.582%	$179.6404	$179.64	$179.65	$179.60
Purchase #2	$247.51	13.478%	$280.8694	$280.87	$280.85	$280.90
Purchase #3	$110.91	5.577%	$117.0955	$117.10	$117.10	$117.10
Purchase #4	$146.93	7.312%	$157.6735	$157.67	$157.65	$157.70
Purchase #5	$203.54	4.734%	$213.1756	$213.18	$213.20	$213.20
Purchase #6	$104.49	6.316%	$111.0896	$111.09	$111.10	$111.10
Purchase #7	$14.43	10.215%	$15.904	$15.90	$15.90	$15.90
7 purchase totals =	$994.79		$1,075.4480	$1,075.45	$1,075.45	$1,075.50