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	$127.44	4.340%	$132.9709	$132.97	$132.95	$133.00
Purchase #2	$162.47	11.106%	$180.5139	$180.51	$180.50	$180.50
Purchase #3	$100.25	11.427%	$111.7056	$111.71	$111.70	$111.70
Purchase #4	$249.65	9.874%	$274.3004	$274.30	$274.30	$274.30
Purchase #5	$16.63	13.652%	$18.9003	$18.90	$18.90	$18.90
Purchase #6	$111.96	7.588%	$120.4555	$120.46	$120.45	$120.50
Purchase #7	$240.66	8.722%	$261.6504	$261.65	$261.65	$261.70
7 purchase totals =	$1,009.06		$1,100.4970	$1,100.50	$1,100.45	$1,100.60