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	$57.96	9.666%	$63.5624	$63.56	$63.55	$63.60
Purchase #2	$203.27	10.749%	$225.1195	$225.12	$225.10	$225.10
Purchase #3	$132.73	3.703%	$137.645	$137.65	$137.65	$137.60
Purchase #4	$32.25	4.575%	$33.7254	$33.73	$33.75	$33.70
Purchase #5	$127.30	13.627%	$144.6472	$144.65	$144.65	$144.60
Purchase #6	$229.45	5.238%	$241.4686	$241.47	$241.45	$241.50
Purchase #7	$76.32	13.179%	$86.3782	$86.38	$86.40	$86.40
7 purchase totals =	$859.28		$932.5463	$932.56	$932.55	$932.50