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	$148.49	13.112%	$167.96	$167.96	$167.95	$168.00
Purchase #2	$122.61	12.465%	$137.8933	$137.89	$137.90	$137.90
Purchase #3	$213.50	13.532%	$242.3908	$242.39	$242.40	$242.40
Purchase #4	$45.55	13.226%	$51.5744	$51.57	$51.55	$51.60
Purchase #5	$25.94	11.422%	$28.9029	$28.90	$28.90	$28.90
Purchase #6	$119.42	9.710%	$131.0157	$131.02	$131.00	$131.00
Purchase #7	$213.51	11.747%	$238.591	$238.59	$238.60	$238.60
7 purchase totals =	$889.02		$998.3281	$998.32	$998.30	$998.40