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	$109.49	5.522%	$115.536	$115.54	$115.55	$115.50
Purchase #2	$240.29	4.275%	$250.5624	$250.56	$250.55	$250.60
Purchase #3	$157.74	4.338%	$164.5828	$164.58	$164.60	$164.60
Purchase #4	$119.45	5.531%	$126.0568	$126.06	$126.05	$126.10
Purchase #5	$11.89	13.210%	$13.4607	$13.46	$13.45	$13.50
Purchase #6	$96.54	11.389%	$107.5349	$107.53	$107.55	$107.50
Purchase #7	$86.82	12.752%	$97.8913	$97.89	$97.90	$97.90
7 purchase totals =	$822.22		$875.6249	$875.62	$875.65	$875.70