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	$41.54	5.629%	$43.8783	$43.88	$43.90	$43.90
Purchase #2	$63.96	5.320%	$67.3627	$67.36	$67.35	$67.40
Purchase #3	$227.99	12.463%	$256.4044	$256.40	$256.40	$256.40
Purchase #4	$206.89	3.561%	$214.2574	$214.26	$214.25	$214.30
Purchase #5	$75.31	13.290%	$85.3187	$85.32	$85.30	$85.30
Purchase #6	$248.47	7.605%	$267.3661	$267.37	$267.35	$267.40
Purchase #7	$241.48	10.257%	$266.2486	$266.25	$266.25	$266.20
7 purchase totals =	$1,105.64		$1,200.8362	$1,200.84	$1,200.80	$1,200.90