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	$52.51	9.578%	$57.5394	$57.54	$57.55	$57.50
Purchase #2	$200.29	13.542%	$227.4133	$227.41	$227.40	$227.40
Purchase #3	$170.85	6.562%	$182.0612	$182.06	$182.05	$182.10
Purchase #4	$143.65	9.484%	$157.2738	$157.27	$157.25	$157.30
Purchase #5	$13.93	3.803%	$14.4598	$14.46	$14.45	$14.50
Purchase #6	$237.49	13.226%	$268.9004	$268.90	$268.90	$268.90
Purchase #7	$43.83	4.750%	$45.9119	$45.91	$45.90	$45.90
7 purchase totals =	$862.55		$953.5598	$953.55	$953.50	$953.60