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 $58.96   10.600%   $65.2098   $65.21   $65.20   $65.20  
  Purchase #2 $187.41   3.462%   $193.8981   $193.90   $193.90   $193.90  
  Purchase #3 $34.87   12.197%   $39.1231   $39.12   $39.10   $39.10  
  Purchase #4 $59.86   7.626%   $64.4249   $64.42   $64.40   $64.40  
  Purchase #5 $220.35   5.256%   $231.9316   $231.93   $231.95   $231.90  
  Purchase #6 $213.79   13.276%   $242.1728   $242.17   $242.15   $242.20  
  Purchase #7 $22.49   12.481%   $25.297   $25.30   $25.30   $25.30  
  7 purchase totals = $797.73       $862.0573   $862.05   $862.00   $862.00