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 $74.43   13.803%   $84.7036   $84.70   $84.70   $84.70  
  Purchase #2 $125.30   9.165%   $136.7837   $136.78   $136.80   $136.80  
  Purchase #3 $54.35   4.713%   $56.9115   $56.91   $56.90   $56.90  
  Purchase #4 $75.91   9.258%   $82.9377   $82.94   $82.95   $82.90  
  Purchase #5 $58.96   3.547%   $61.0513   $61.05   $61.05   $61.10  
  Purchase #6 $186.85   4.871%   $195.9515   $195.95   $195.95   $196.00  
  Purchase #7 $123.74   8.825%   $134.6601   $134.66   $134.65   $134.70  
  7 purchase totals = $699.54       $752.9994   $752.99   $753.00   $753.10