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	$92.38	6.586%	$98.4641	$98.46	$98.45	$98.50
Purchase #2	$82.94	8.225%	$89.7618	$89.76	$89.75	$89.80
Purchase #3	$30.50	7.799%	$32.8787	$32.88	$32.90	$32.90
Purchase #4	$94.57	11.477%	$105.4238	$105.42	$105.40	$105.40
Purchase #5	$125.81	11.291%	$140.0152	$140.02	$140.00	$140.00
Purchase #6	$97.61	11.354%	$108.6926	$108.69	$108.70	$108.70
Purchase #7	$114.66	6.146%	$121.707	$121.71	$121.70	$121.70
7 purchase totals =	$638.47		$696.9432	$696.94	$696.90	$697.00