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	$95.69	3.335%	$98.8813	$98.88	$98.90	$98.90
Purchase #2	$56.88	3.754%	$59.0153	$59.02	$59.00	$59.00
Purchase #3	$71.56	13.305%	$81.0811	$81.08	$81.10	$81.10
Purchase #4	$183.73	11.206%	$204.3188	$204.32	$204.30	$204.30
Purchase #5	$77.59	11.433%	$86.4609	$86.46	$86.45	$86.50
Purchase #6	$198.94	12.546%	$223.899	$223.90	$223.90	$223.90
Purchase #7	$146.89	11.545%	$163.8485	$163.85	$163.85	$163.80
7 purchase totals =	$831.28		$917.5049	$917.51	$917.50	$917.50