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	$205.52	8.796%	$223.5975	$223.60	$223.60	$223.60
Purchase #2	$109.79	8.265%	$118.8641	$118.86	$118.85	$118.90
Purchase #3	$129.98	9.194%	$141.9304	$141.93	$141.95	$141.90
Purchase #4	$76.51	13.546%	$86.874	$86.87	$86.85	$86.90
Purchase #5	$195.39	10.128%	$215.1791	$215.18	$215.20	$215.20
Purchase #6	$185.32	12.266%	$208.0514	$208.05	$208.05	$208.10
Purchase #7	$65.43	8.293%	$70.8561	$70.86	$70.85	$70.90
7 purchase totals =	$967.94		$1,065.3526	$1,065.35	$1,065.35	$1,065.50