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	$37.91	9.369%	$41.4618	$41.46	$41.45	$41.50
Purchase #2	$98.90	4.452%	$103.303	$103.30	$103.30	$103.30
Purchase #3	$133.79	7.583%	$143.9353	$143.94	$143.95	$143.90
Purchase #4	$140.95	10.605%	$155.8977	$155.90	$155.90	$155.90
Purchase #5	$126.58	3.376%	$130.8533	$130.85	$130.85	$130.90
Purchase #6	$99.74	5.700%	$105.4252	$105.43	$105.45	$105.40
Purchase #7	$210.88	6.381%	$224.3363	$224.34	$224.35	$224.30
7 purchase totals =	$848.75		$905.2126	$905.22	$905.25	$905.20