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	$164.87	12.784%	$185.947	$185.95	$185.95	$185.90
Purchase #2	$190.86	7.151%	$204.5084	$204.51	$204.50	$204.50
Purchase #3	$214.44	12.742%	$241.7639	$241.76	$241.75	$241.80
Purchase #4	$123.95	5.806%	$131.1465	$131.15	$131.15	$131.10
Purchase #5	$212.94	4.541%	$222.6096	$222.61	$222.60	$222.60
Purchase #6	$47.56	8.766%	$51.7291	$51.73	$51.75	$51.70
Purchase #7	$205.51	7.139%	$220.1814	$220.18	$220.20	$220.20
7 purchase totals =	$1,160.13		$1,257.8859	$1,257.89	$1,257.90	$1,257.80