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	$63.78	5.682%	$67.404	$67.40	$67.40	$67.40
Purchase #2	$75.47	7.769%	$81.3333	$81.33	$81.35	$81.30
Purchase #3	$178.83	11.190%	$198.8411	$198.84	$198.85	$198.80
Purchase #4	$141.81	4.725%	$148.5105	$148.51	$148.50	$148.50
Purchase #5	$232.30	3.386%	$240.1657	$240.17	$240.15	$240.20
Purchase #6	$85.32	11.257%	$94.9245	$94.92	$94.90	$94.90
Purchase #7	$40.37	13.366%	$45.7659	$45.77	$45.75	$45.80
7 purchase totals =	$817.88		$876.9450	$876.94	$876.90	$876.90