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	$50.50	8.870%	$54.9794	$54.98	$55.00	$55.00
Purchase #2	$16.85	6.177%	$17.8908	$17.89	$17.90	$17.90
Purchase #3	$233.43	8.132%	$252.4125	$252.41	$252.40	$252.40
Purchase #4	$88.71	9.624%	$97.2475	$97.25	$97.25	$97.20
Purchase #5	$69.92	12.243%	$78.4803	$78.48	$78.50	$78.50
Purchase #6	$57.94	3.203%	$59.7958	$59.80	$59.80	$59.80
Purchase #7	$171.88	11.352%	$191.3918	$191.39	$191.40	$191.40
7 purchase totals =	$689.23		$752.1981	$752.20	$752.25	$752.20