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	$81.54	11.759%	$91.1283	$91.13	$91.15	$91.10
Purchase #2	$181.52	8.338%	$196.6551	$196.66	$196.65	$196.70
Purchase #3	$63.37	12.833%	$71.5023	$71.50	$71.50	$71.50
Purchase #4	$126.49	4.387%	$132.0391	$132.04	$132.05	$132.00
Purchase #5	$232.63	13.241%	$263.4325	$263.43	$263.45	$263.40
Purchase #6	$195.30	8.187%	$211.2892	$211.29	$211.30	$211.30
Purchase #7	$164.25	10.706%	$181.8346	$181.83	$181.85	$181.80
7 purchase totals =	$1,045.10		$1,147.8811	$1,147.88	$1,147.95	$1,147.80