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 $66.47   4.528%   $69.4798   $69.48   $69.50   $69.50  
  Purchase #2 $217.59   6.850%   $232.4949   $232.49   $232.50   $232.50  
  Purchase #3 $118.69   11.285%   $132.0842   $132.08   $132.10   $132.10  
  Purchase #4 $228.43   10.706%   $252.8857   $252.89   $252.90   $252.90  
  Purchase #5 $203.69   10.714%   $225.5133   $225.51   $225.50   $225.50  
  Purchase #6 $117.48   12.588%   $132.2684   $132.27   $132.25   $132.30  
  Purchase #7 $74.51   4.433%   $77.813   $77.81   $77.80   $77.80  
  7 purchase totals = $1,026.86       $1,122.5393   $1,122.53   $1,122.55   $1,122.60