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	$214.32	8.487%	$232.5093	$232.51	$232.50	$232.50
Purchase #2	$165.28	12.123%	$185.3169	$185.32	$185.30	$185.30
Purchase #3	$115.38	4.601%	$120.6886	$120.69	$120.70	$120.70
Purchase #4	$230.91	12.426%	$259.6029	$259.60	$259.60	$259.60
Purchase #5	$29.73	7.226%	$31.8783	$31.88	$31.90	$31.90
Purchase #6	$36.36	12.434%	$40.881	$40.88	$40.90	$40.90
Purchase #7	$77.28	11.219%	$85.95	$85.95	$85.95	$86.00
7 purchase totals =	$869.26		$956.8270	$956.83	$956.85	$956.90