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	$150.88	8.865%	$164.2555	$164.26	$164.25	$164.30
Purchase #2	$172.70	13.294%	$195.6587	$195.66	$195.65	$195.70
Purchase #3	$65.83	9.280%	$71.939	$71.94	$71.95	$71.90
Purchase #4	$123.36	11.625%	$137.7006	$137.70	$137.70	$137.70
Purchase #5	$63.47	5.147%	$66.7368	$66.74	$66.75	$66.70
Purchase #6	$153.83	11.386%	$171.3451	$171.35	$171.35	$171.30
Purchase #7	$88.77	13.577%	$100.8223	$100.82	$100.80	$100.80
7 purchase totals =	$818.84		$908.4580	$908.47	$908.45	$908.40