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 $75.25   13.872%   $85.6887   $85.69   $85.70   $85.70  
  Purchase #2 $12.47   10.138%   $13.7342   $13.73   $13.75   $13.70  
  Purchase #3 $209.78   12.339%   $235.6648   $235.66   $235.65   $235.70  
  Purchase #4 $52.59   7.610%   $56.5921   $56.59   $56.60   $56.60  
  Purchase #5 $78.52   5.710%   $83.0035   $83.00   $83.00   $83.00  
  Purchase #6 $24.91   5.564%   $26.296   $26.30   $26.30   $26.30  
  Purchase #7 $221.56   4.791%   $232.1749   $232.17   $232.15   $232.20  
  7 purchase totals = $675.08       $733.1542   $733.14   $733.15   $733.20