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	$234.42	13.132%	$265.204	$265.20	$265.20	$265.20
Purchase #2	$211.51	5.743%	$223.657	$223.66	$223.65	$223.70
Purchase #3	$30.75	4.388%	$32.0993	$32.10	$32.10	$32.10
Purchase #4	$142.83	6.699%	$152.3982	$152.40	$152.40	$152.40
Purchase #5	$96.53	8.706%	$104.9339	$104.93	$104.95	$104.90
Purchase #6	$190.89	4.455%	$199.3941	$199.39	$199.40	$199.40
Purchase #7	$6.89	4.326%	$7.1881	$7.19	$7.20	$7.20
7 purchase totals =	$913.82		$984.8746	$984.87	$984.90	$984.90