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	$38.36	7.533%	$41.2497	$41.25	$41.25	$41.20
Purchase #2	$15.97	11.231%	$17.7636	$17.76	$17.75	$17.80
Purchase #3	$137.45	12.462%	$154.579	$154.58	$154.60	$154.60
Purchase #4	$102.63	3.163%	$105.8762	$105.88	$105.90	$105.90
Purchase #5	$57.25	9.145%	$62.4855	$62.49	$62.50	$62.50
Purchase #6	$78.47	11.671%	$87.6282	$87.63	$87.65	$87.60
Purchase #7	$29.43	11.725%	$32.8807	$32.88	$32.90	$32.90
7 purchase totals =	$459.56		$502.4629	$502.47	$502.55	$502.50