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	$135.51	5.804%	$143.375	$143.38	$143.40	$143.40
Purchase #2	$30.83	3.476%	$31.9017	$31.90	$31.90	$31.90
Purchase #3	$29.60	6.666%	$31.5731	$31.57	$31.55	$31.60
Purchase #4	$30.74	5.671%	$32.4833	$32.48	$32.50	$32.50
Purchase #5	$138.43	5.415%	$145.926	$145.93	$145.95	$145.90
Purchase #6	$216.93	13.122%	$245.3956	$245.40	$245.40	$245.40
Purchase #7	$119.31	6.710%	$127.3157	$127.32	$127.30	$127.30
7 purchase totals =	$701.35		$757.9704	$757.98	$758.00	$758.00