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	$65.54	3.240%	$67.6635	$67.66	$67.65	$67.70
Purchase #2	$121.53	8.390%	$131.7264	$131.73	$131.75	$131.70
Purchase #3	$172.31	10.681%	$190.7144	$190.71	$190.70	$190.70
Purchase #4	$219.33	11.576%	$244.7196	$244.72	$244.70	$244.70
Purchase #5	$130.80	5.481%	$137.9691	$137.97	$137.95	$138.00
Purchase #6	$129.49	8.599%	$140.6248	$140.62	$140.60	$140.60
Purchase #7	$96.71	9.440%	$105.8394	$105.84	$105.85	$105.80
7 purchase totals =	$935.71		$1,019.2572	$1,019.25	$1,019.20	$1,019.20