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	$98.67	11.393%	$109.9115	$109.91	$109.90	$109.90
Purchase #2	$36.90	12.423%	$41.4841	$41.48	$41.50	$41.50
Purchase #3	$34.50	12.395%	$38.7763	$38.78	$38.80	$38.80
Purchase #4	$220.75	8.227%	$238.9111	$238.91	$238.90	$238.90
Purchase #5	$133.98	8.443%	$145.2919	$145.29	$145.30	$145.30
Purchase #6	$192.55	8.288%	$208.5085	$208.51	$208.50	$208.50
Purchase #7	$184.58	6.383%	$196.3617	$196.36	$196.35	$196.40
7 purchase totals =	$901.93		$979.2451	$979.24	$979.25	$979.30