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	$57.36	7.599%	$61.7188	$61.72	$61.70	$61.70
Purchase #2	$113.57	12.491%	$127.756	$127.76	$127.75	$127.80
Purchase #3	$13.30	9.291%	$14.5357	$14.54	$14.55	$14.50
Purchase #4	$182.97	4.121%	$190.5102	$190.51	$190.50	$190.50
Purchase #5	$227.84	11.119%	$253.1735	$253.17	$253.15	$253.20
Purchase #6	$176.47	5.634%	$186.4123	$186.41	$186.40	$186.40
Purchase #7	$137.38	4.635%	$143.7476	$143.75	$143.75	$143.70
7 purchase totals =	$908.89		$977.8541	$977.86	$977.80	$977.80