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	$108.98	3.846%	$113.1714	$113.17	$113.15	$113.20
Purchase #2	$119.32	12.189%	$133.8639	$133.86	$133.85	$133.90
Purchase #3	$36.96	3.292%	$38.1767	$38.18	$38.20	$38.20
Purchase #4	$210.44	3.178%	$217.1278	$217.13	$217.15	$217.10
Purchase #5	$90.57	11.425%	$100.9176	$100.92	$100.90	$100.90
Purchase #6	$37.30	13.743%	$42.4261	$42.43	$42.45	$42.40
Purchase #7	$222.93	3.839%	$231.4883	$231.49	$231.50	$231.50
7 purchase totals =	$826.50		$877.1718	$877.18	$877.20	$877.20