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	$247.86	4.702%	$259.5144	$259.51	$259.50	$259.50
Purchase #2	$150.83	11.411%	$168.0412	$168.04	$168.05	$168.00
Purchase #3	$87.32	6.385%	$92.8954	$92.90	$92.90	$92.90
Purchase #4	$172.72	4.168%	$179.919	$179.92	$179.90	$179.90
Purchase #5	$150.35	9.615%	$164.8062	$164.81	$164.80	$164.80
Purchase #6	$43.96	11.214%	$48.8897	$48.89	$48.90	$48.90
Purchase #7	$170.36	10.559%	$188.3483	$188.35	$188.35	$188.30
7 purchase totals =	$1,023.40		$1,102.4142	$1,102.42	$1,102.40	$1,102.30