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 $57.68   7.583%   $62.0539   $62.05   $62.05   $62.10  
  Purchase #2 $174.63   13.819%   $198.7621   $198.76   $198.75   $198.80  
  Purchase #3 $178.92   9.825%   $196.4989   $196.50   $196.50   $196.50  
  Purchase #4 $65.58   6.337%   $69.7358   $69.74   $69.75   $69.70  
  Purchase #5 $231.34   5.393%   $243.8162   $243.82   $243.80   $243.80  
  Purchase #6 $213.81   4.779%   $224.028   $224.03   $224.05   $224.00  
  Purchase #7 $207.84   6.131%   $220.5827   $220.58   $220.60   $220.60  
  7 purchase totals = $1,129.80       $1,215.4776   $1,215.48   $1,215.50   $1,215.50