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	$85.93	5.859%	$90.9646	$90.96	$90.95	$91.00
Purchase #2	$242.46	6.238%	$257.5847	$257.58	$257.60	$257.60
Purchase #3	$65.33	7.218%	$70.0455	$70.05	$70.05	$70.00
Purchase #4	$77.55	6.223%	$82.3759	$82.38	$82.40	$82.40
Purchase #5	$186.86	8.812%	$203.3261	$203.33	$203.35	$203.30
Purchase #6	$18.72	9.503%	$20.499	$20.50	$20.50	$20.50
Purchase #7	$126.59	13.549%	$143.7417	$143.74	$143.75	$143.70
7 purchase totals =	$803.44		$868.5375	$868.54	$868.60	$868.50