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	$29.75	5.637%	$31.427	$31.43	$31.45	$31.40
Purchase #2	$118.50	4.604%	$123.9557	$123.96	$123.95	$124.00
Purchase #3	$162.71	8.546%	$176.6152	$176.62	$176.60	$176.60
Purchase #4	$208.27	7.811%	$224.538	$224.54	$224.55	$224.50
Purchase #5	$86.96	3.285%	$89.8166	$89.82	$89.80	$89.80
Purchase #6	$158.75	5.507%	$167.4924	$167.49	$167.50	$167.50
Purchase #7	$182.59	12.391%	$205.2147	$205.21	$205.20	$205.20
7 purchase totals =	$947.53		$1,019.0596	$1,019.07	$1,019.05	$1,019.00