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	$57.25	4.509%	$59.8314	$59.83	$59.85	$59.80
Purchase #2	$205.41	5.238%	$216.1694	$216.17	$216.15	$216.20
Purchase #3	$42.91	13.189%	$48.5694	$48.57	$48.55	$48.60
Purchase #4	$41.88	3.520%	$43.3542	$43.35	$43.35	$43.40
Purchase #5	$119.52	4.316%	$124.6785	$124.68	$124.70	$124.70
Purchase #6	$141.51	7.609%	$152.2775	$152.28	$152.30	$152.30
Purchase #7	$40.25	5.732%	$42.5571	$42.56	$42.55	$42.60
7 purchase totals =	$648.73		$687.4375	$687.44	$687.45	$687.60