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	$33.56	10.526%	$37.0925	$37.09	$37.10	$37.10
Purchase #2	$154.32	9.102%	$168.3662	$168.37	$168.35	$168.40
Purchase #3	$51.78	6.802%	$55.3021	$55.30	$55.30	$55.30
Purchase #4	$67.48	8.176%	$72.9972	$73.00	$73.00	$73.00
Purchase #5	$12.90	4.111%	$13.4303	$13.43	$13.45	$13.40
Purchase #6	$45.97	5.398%	$48.4515	$48.45	$48.45	$48.50
Purchase #7	$162.78	7.426%	$174.868	$174.87	$174.85	$174.90
7 purchase totals =	$528.79		$570.5078	$570.51	$570.50	$570.60