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	$55.84	7.102%	$59.8058	$59.81	$59.80	$59.80
Purchase #2	$53.80	7.698%	$57.9415	$57.94	$57.95	$57.90
Purchase #3	$104.55	3.280%	$107.9792	$107.98	$108.00	$108.00
Purchase #4	$58.72	12.447%	$66.0289	$66.03	$66.05	$66.00
Purchase #5	$59.51	11.677%	$66.459	$66.46	$66.45	$66.50
Purchase #6	$212.91	13.854%	$242.4066	$242.41	$242.40	$242.40
Purchase #7	$119.58	12.665%	$134.7248	$134.72	$134.70	$134.70
7 purchase totals =	$664.91		$735.3458	$735.35	$735.35	$735.30