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	$104.25	8.692%	$113.3114	$113.31	$113.30	$113.30
Purchase #2	$187.89	10.124%	$206.912	$206.91	$206.90	$206.90
Purchase #3	$106.72	9.496%	$116.8541	$116.85	$116.85	$116.90
Purchase #4	$225.47	12.872%	$254.4925	$254.49	$254.50	$254.50
Purchase #5	$133.86	12.235%	$150.2378	$150.24	$150.25	$150.20
Purchase #6	$97.69	4.733%	$102.3137	$102.31	$102.30	$102.30
Purchase #7	$67.69	7.645%	$72.8649	$72.86	$72.85	$72.90
7 purchase totals =	$923.57		$1,016.9864	$1,016.97	$1,016.95	$1,017.00