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	$138.45	9.319%	$151.3522	$151.35	$151.35	$151.40
Purchase #2	$117.96	11.461%	$131.4794	$131.48	$131.50	$131.50
Purchase #3	$210.26	12.153%	$235.8129	$235.81	$235.80	$235.80
Purchase #4	$175.25	8.717%	$190.5265	$190.53	$190.55	$190.50
Purchase #5	$192.37	12.500%	$216.4163	$216.42	$216.40	$216.40
Purchase #6	$84.40	6.661%	$90.0219	$90.02	$90.00	$90.00
Purchase #7	$41.66	4.397%	$43.4918	$43.49	$43.50	$43.50
7 purchase totals =	$960.35		$1,059.1010	$1,059.10	$1,059.10	$1,059.10