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 $115.49   8.407%   $125.1992   $125.20   $125.20   $125.20  
  Purchase #2 $122.94   10.818%   $136.2396   $136.24   $136.25   $136.20  
  Purchase #3 $231.77   6.372%   $246.5384   $246.54   $246.55   $246.50  
  Purchase #4 $131.52   8.536%   $142.7465   $142.75   $142.75   $142.70  
  Purchase #5 $71.35   4.485%   $74.55   $74.55   $74.55   $74.60  
  Purchase #6 $217.36   13.580%   $246.8775   $246.88   $246.90   $246.90  
  Purchase #7 $46.98   12.495%   $52.8502   $52.85   $52.85   $52.90  
  7 purchase totals = $937.41       $1,025.0014   $1,025.01   $1,025.05   $1,025.00