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	$241.42	11.164%	$268.3721	$268.37	$268.35	$268.40
Purchase #2	$140.96	8.486%	$152.9219	$152.92	$152.90	$152.90
Purchase #3	$122.92	4.333%	$128.2461	$128.25	$128.25	$128.20
Purchase #4	$185.39	11.438%	$206.5949	$206.59	$206.60	$206.60
Purchase #5	$46.49	6.303%	$49.4203	$49.42	$49.40	$49.40
Purchase #6	$91.31	13.467%	$103.6067	$103.61	$103.60	$103.60
Purchase #7	$164.89	12.719%	$185.8624	$185.86	$185.85	$185.90
7 purchase totals =	$993.38		$1,095.0244	$1,095.02	$1,094.95	$1,095.00