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 $92.33   4.711%   $96.6797   $96.68   $96.70   $96.70  
  Purchase #2 $119.70   3.264%   $123.607   $123.61   $123.60   $123.60  
  Purchase #3 $164.61   6.832%   $175.8562   $175.86   $175.85   $175.90  
  Purchase #4 $191.44   10.548%   $211.6331   $211.63   $211.65   $211.60  
  Purchase #5 $179.58   4.793%   $188.1873   $188.19   $188.20   $188.20  
  Purchase #6 $28.66   6.415%   $30.4985   $30.50   $30.50   $30.50  
  Purchase #7 $197.86   5.211%   $208.1705   $208.17   $208.15   $208.20  
  7 purchase totals = $974.18       $1,034.6323   $1,034.64   $1,034.65   $1,034.70