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	$82.81	4.714%	$86.7137	$86.71	$86.70	$86.70
Purchase #2	$231.80	12.102%	$259.8524	$259.85	$259.85	$259.90
Purchase #3	$62.59	7.248%	$67.1265	$67.13	$67.15	$67.10
Purchase #4	$131.60	4.531%	$137.5628	$137.56	$137.55	$137.60
Purchase #5	$241.86	9.625%	$265.139	$265.14	$265.15	$265.10
Purchase #6	$206.57	8.424%	$223.9715	$223.97	$223.95	$224.00
Purchase #7	$130.67	13.731%	$148.6123	$148.61	$148.60	$148.60
7 purchase totals =	$1,087.90		$1,188.9782	$1,188.97	$1,188.95	$1,189.00