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 $60.54   3.637%   $62.7418   $62.74   $62.75   $62.70  
  Purchase #2 $221.62   4.663%   $231.9541   $231.95   $231.95   $232.00  
  Purchase #3 $121.77   3.307%   $125.7969   $125.80   $125.80   $125.80  
  Purchase #4 $234.71   9.651%   $257.3619   $257.36   $257.35   $257.40  
  Purchase #5 $181.75   10.605%   $201.0246   $201.02   $201.00   $201.00  
  Purchase #6 $128.36   7.851%   $138.4375   $138.44   $138.45   $138.40  
  Purchase #7 $128.68   3.396%   $133.05   $133.05   $133.05   $133.10  
  7 purchase totals = $1,077.43       $1,150.3668   $1,150.36   $1,150.35   $1,150.40