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	$172.78	5.264%	$181.8751	$181.88	$181.90	$181.90
Purchase #2	$193.82	3.391%	$200.3924	$200.39	$200.40	$200.40
Purchase #3	$55.76	11.273%	$62.0458	$62.05	$62.05	$62.00
Purchase #4	$192.48	11.527%	$214.6672	$214.67	$214.65	$214.70
Purchase #5	$72.77	6.434%	$77.452	$77.45	$77.45	$77.50
Purchase #6	$21.83	6.248%	$23.1939	$23.19	$23.20	$23.20
Purchase #7	$153.38	12.633%	$172.7565	$172.76	$172.75	$172.80
7 purchase totals =	$862.82		$932.3829	$932.39	$932.40	$932.50