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	$206.85	3.386%	$213.8539	$213.85	$213.85	$213.90
Purchase #2	$100.75	5.138%	$105.9265	$105.93	$105.95	$105.90
Purchase #3	$244.82	4.504%	$255.8467	$255.85	$255.85	$255.80
Purchase #4	$196.88	6.756%	$210.1812	$210.18	$210.20	$210.20
Purchase #5	$35.48	13.812%	$40.3805	$40.38	$40.40	$40.40
Purchase #6	$242.63	10.576%	$268.2905	$268.29	$268.30	$268.30
Purchase #7	$5.48	9.102%	$5.9788	$5.98	$6.00	$6.00
7 purchase totals =	$1,032.89		$1,100.4581	$1,100.46	$1,100.55	$1,100.50