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	$206.74	5.659%	$218.4394	$218.44	$218.45	$218.40
Purchase #2	$62.63	6.837%	$66.912	$66.91	$66.90	$66.90
Purchase #3	$203.63	3.397%	$210.5473	$210.55	$210.55	$210.50
Purchase #4	$178.76	6.296%	$190.0147	$190.01	$190.00	$190.00
Purchase #5	$34.79	4.410%	$36.3242	$36.32	$36.30	$36.30
Purchase #6	$39.25	6.711%	$41.8841	$41.88	$41.90	$41.90
Purchase #7	$114.79	11.353%	$127.8221	$127.82	$127.80	$127.80
7 purchase totals =	$840.59		$891.9438	$891.93	$891.90	$891.80