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	$112.28	3.365%	$116.0582	$116.06	$116.05	$116.10
Purchase #2	$29.57	10.555%	$32.6911	$32.69	$32.70	$32.70
Purchase #3	$129.51	10.633%	$143.2808	$143.28	$143.30	$143.30
Purchase #4	$113.61	11.753%	$126.9626	$126.96	$126.95	$127.00
Purchase #5	$70.37	8.655%	$76.4605	$76.46	$76.45	$76.50
Purchase #6	$226.28	12.859%	$255.3773	$255.38	$255.40	$255.40
Purchase #7	$167.58	8.609%	$182.007	$182.01	$182.00	$182.00
7 purchase totals =	$849.20		$932.8375	$932.84	$932.85	$933.00