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	$31.97	12.338%	$35.9145	$35.91	$35.90	$35.90
Purchase #2	$189.33	12.556%	$213.1023	$213.10	$213.10	$213.10
Purchase #3	$158.25	10.237%	$174.4501	$174.45	$174.45	$174.50
Purchase #4	$204.88	8.548%	$222.3931	$222.39	$222.40	$222.40
Purchase #5	$176.26	11.186%	$195.9764	$195.98	$196.00	$196.00
Purchase #6	$49.51	12.340%	$55.6195	$55.62	$55.60	$55.60
Purchase #7	$131.38	9.241%	$143.5208	$143.52	$143.50	$143.50
7 purchase totals =	$941.58		$1,040.9767	$1,040.97	$1,040.95	$1,041.00