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 $58.96   5.246%   $62.053   $62.05   $62.05   $62.10  
  Purchase #2 $20.67   7.769%   $22.2759   $22.28   $22.30   $22.30  
  Purchase #3 $67.69   11.864%   $75.7207   $75.72   $75.70   $75.70  
  Purchase #4 $217.40   3.680%   $225.4003   $225.40   $225.40   $225.40  
  Purchase #5 $228.59   13.727%   $259.9685   $259.97   $259.95   $260.00  
  Purchase #6 $126.28   13.380%   $143.1763   $143.18   $143.20   $143.20  
  Purchase #7 $7.91   13.597%   $8.9855   $8.99   $9.00   $9.00  
  7 purchase totals = $727.50       $797.5802   $797.59   $797.60   $797.70