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 $63.46   10.520%   $70.136   $70.14   $70.15   $70.10  
  Purchase #2 $172.87   3.179%   $178.3655   $178.37   $178.35   $178.40  
  Purchase #3 $128.29   6.466%   $136.5852   $136.59   $136.60   $136.60  
  Purchase #4 $141.49   3.587%   $146.5652   $146.57   $146.55   $146.60  
  Purchase #5 $208.96   13.359%   $236.875   $236.88   $236.90   $236.90  
  Purchase #6 $82.49   13.181%   $93.363   $93.36   $93.35   $93.40  
  Purchase #7 $165.60   5.752%   $175.1253   $175.13   $175.15   $175.10  
  7 purchase totals = $963.16       $1,037.0152   $1,037.04   $1,037.05   $1,037.10