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	$61.51	8.300%	$66.6153	$66.62	$66.60	$66.60
Purchase #2	$18.41	12.594%	$20.7286	$20.73	$20.75	$20.70
Purchase #3	$74.83	10.131%	$82.411	$82.41	$82.40	$82.40
Purchase #4	$243.53	8.363%	$263.8964	$263.90	$263.90	$263.90
Purchase #5	$249.64	5.262%	$262.7761	$262.78	$262.80	$262.80
Purchase #6	$143.86	9.421%	$157.4131	$157.41	$157.40	$157.40
Purchase #7	$169.38	10.105%	$186.4958	$186.50	$186.50	$186.50
7 purchase totals =	$961.16		$1,040.3363	$1,040.35	$1,040.35	$1,040.30