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 $67.96   12.835%   $76.6827   $76.68   $76.70   $76.70  
  Purchase #2 $191.62   10.843%   $212.3974   $212.40   $212.40   $212.40  
  Purchase #3 $47.83   13.225%   $54.1555   $54.16   $54.15   $54.20  
  Purchase #4 $170.34   5.452%   $179.6269   $179.63   $179.65   $179.60  
  Purchase #5 $236.85   4.351%   $247.1553   $247.16   $247.15   $247.20  
  Purchase #6 $223.50   5.194%   $235.1086   $235.11   $235.10   $235.10  
  Purchase #7 $240.82   6.775%   $257.1356   $257.14   $257.15   $257.10  
  7 purchase totals = $1,178.92       $1,262.2620   $1,262.28   $1,262.30   $1,262.30