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	$190.32	3.107%	$196.2332	$196.23	$196.25	$196.20
Purchase #2	$64.66	13.561%	$73.4285	$73.43	$73.45	$73.40
Purchase #3	$48.86	4.398%	$51.0089	$51.01	$51.00	$51.00
Purchase #4	$102.28	10.728%	$113.2526	$113.25	$113.25	$113.30
Purchase #5	$135.60	11.287%	$150.9052	$150.91	$150.90	$150.90
Purchase #6	$43.75	3.624%	$45.3355	$45.34	$45.35	$45.30
Purchase #7	$163.89	4.861%	$171.8567	$171.86	$171.85	$171.90
7 purchase totals =	$749.36		$802.0206	$802.03	$802.05	$802.00