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 $94.66   12.249%   $106.2549   $106.25   $106.25   $106.30  
  Purchase #2 $211.49   12.309%   $237.5223   $237.52   $237.50   $237.50  
  Purchase #3 $213.47   13.671%   $242.6535   $242.65   $242.65   $242.70  
  Purchase #4 $83.54   3.385%   $86.3678   $86.37   $86.35   $86.40  
  Purchase #5 $19.90   10.514%   $21.9923   $21.99   $22.00   $22.00  
  Purchase #6 $17.64   3.786%   $18.3079   $18.31   $18.30   $18.30  
  Purchase #7 $35.75   11.274%   $39.7805   $39.78   $39.80   $39.80  
  7 purchase totals = $676.45       $752.8792   $752.87   $752.85   $753.00