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 $69.35   10.863%   $76.8835   $76.88   $76.90   $76.90  
  Purchase #2 $219.35   7.294%   $235.3494   $235.35   $235.35   $235.30  
  Purchase #3 $130.96   3.867%   $136.0242   $136.02   $136.00   $136.00  
  Purchase #4 $174.98   12.391%   $196.6618   $196.66   $196.65   $196.70  
  Purchase #5 $7.68   10.216%   $8.4646   $8.46   $8.45   $8.50  
  Purchase #6 $153.56   4.326%   $160.203   $160.20   $160.20   $160.20  
  Purchase #7 $135.64   4.349%   $141.539   $141.54   $141.55   $141.50  
  7 purchase totals = $891.52       $955.1255   $955.11   $955.10   $955.10