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	$117.51	12.169%	$131.8098	$131.81	$131.80	$131.80
Purchase #2	$125.84	13.319%	$142.6006	$142.60	$142.60	$142.60
Purchase #3	$65.40	11.558%	$72.9589	$72.96	$72.95	$73.00
Purchase #4	$162.26	11.378%	$180.7219	$180.72	$180.70	$180.70
Purchase #5	$188.89	13.715%	$214.7963	$214.80	$214.80	$214.80
Purchase #6	$97.33	4.177%	$101.3955	$101.40	$101.40	$101.40
Purchase #7	$89.31	9.611%	$97.8936	$97.89	$97.90	$97.90
7 purchase totals =	$846.54		$942.1766	$942.18	$942.15	$942.20