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	$193.75	8.691%	$210.5888	$210.59	$210.60	$210.60
Purchase #2	$244.96	6.265%	$260.3067	$260.31	$260.30	$260.30
Purchase #3	$60.47	3.492%	$62.5816	$62.58	$62.60	$62.60
Purchase #4	$51.57	12.187%	$57.8548	$57.85	$57.85	$57.90
Purchase #5	$31.48	5.578%	$33.236	$33.24	$33.25	$33.20
Purchase #6	$80.93	10.724%	$89.6089	$89.61	$89.60	$89.60
Purchase #7	$143.59	6.796%	$153.3484	$153.35	$153.35	$153.30
7 purchase totals =	$806.75		$867.5252	$867.53	$867.55	$867.50