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 $101.36   13.192%   $114.7314   $114.73   $114.75   $114.70  
  Purchase #2 $135.86   8.361%   $147.2193   $147.22   $147.20   $147.20  
  Purchase #3 $184.83   7.217%   $198.1692   $198.17   $198.15   $198.20  
  Purchase #4 $82.73   3.683%   $85.7769   $85.78   $85.80   $85.80  
  Purchase #5 $182.93   10.709%   $202.52   $202.52   $202.50   $202.50  
  Purchase #6 $127.48   10.751%   $141.1854   $141.19   $141.20   $141.20  
  Purchase #7 $139.68   4.808%   $146.3958   $146.40   $146.40   $146.40  
  7 purchase totals = $954.87       $1,035.9980   $1,036.01   $1,036.00   $1,036.00