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	$141.85	10.141%	$156.235	$156.24	$156.25	$156.20
Purchase #2	$11.49	11.673%	$12.8312	$12.83	$12.85	$12.80
Purchase #3	$249.44	3.602%	$258.4248	$258.42	$258.40	$258.40
Purchase #4	$51.38	11.567%	$57.3231	$57.32	$57.30	$57.30
Purchase #5	$30.98	11.278%	$34.4739	$34.47	$34.45	$34.50
Purchase #6	$136.98	13.783%	$155.86	$155.86	$155.85	$155.90
Purchase #7	$160.71	8.384%	$174.1839	$174.18	$174.20	$174.20
7 purchase totals =	$782.83		$849.3319	$849.32	$849.30	$849.30