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	$155.90	4.140%	$162.3543	$162.35	$162.35	$162.40
Purchase #2	$234.27	10.103%	$257.9383	$257.94	$257.95	$257.90
Purchase #3	$170.81	9.477%	$186.9977	$187.00	$187.00	$187.00
Purchase #4	$92.82	10.428%	$102.4993	$102.50	$102.50	$102.50
Purchase #5	$58.86	6.834%	$62.8825	$62.88	$62.90	$62.90
Purchase #6	$111.81	4.555%	$116.9029	$116.90	$116.90	$116.90
Purchase #7	$42.66	4.835%	$44.7226	$44.72	$44.70	$44.70
7 purchase totals =	$867.13		$934.2976	$934.29	$934.30	$934.30