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	$78.46	9.363%	$85.8062	$85.81	$85.80	$85.80
Purchase #2	$122.77	12.296%	$137.8658	$137.87	$137.85	$137.90
Purchase #3	$88.86	5.535%	$93.7784	$93.78	$93.80	$93.80
Purchase #4	$118.42	11.714%	$132.2917	$132.29	$132.30	$132.30
Purchase #5	$208.82	8.294%	$226.1395	$226.14	$226.15	$226.10
Purchase #6	$209.78	9.263%	$229.2119	$229.21	$229.20	$229.20
Purchase #7	$143.78	10.166%	$158.3967	$158.40	$158.40	$158.40
7 purchase totals =	$970.89		$1,063.4902	$1,063.50	$1,063.50	$1,063.50