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	$188.84	3.294%	$195.0604	$195.06	$195.05	$195.10
Purchase #2	$35.44	8.535%	$38.4648	$38.46	$38.45	$38.50
Purchase #3	$249.81	11.458%	$278.4332	$278.43	$278.45	$278.40
Purchase #4	$95.78	6.776%	$102.2701	$102.27	$102.25	$102.30
Purchase #5	$38.73	3.321%	$40.0162	$40.02	$40.00	$40.00
Purchase #6	$41.80	11.210%	$46.4858	$46.49	$46.50	$46.50
Purchase #7	$150.29	9.328%	$164.3091	$164.31	$164.30	$164.30
7 purchase totals =	$800.69		$865.0396	$865.04	$865.00	$865.10