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 $222.64   10.779%   $246.6384   $246.64   $246.65   $246.60  
  Purchase #2 $31.95   10.226%   $35.2172   $35.22   $35.20   $35.20  
  Purchase #3 $205.97   3.198%   $212.5569   $212.56   $212.55   $212.60  
  Purchase #4 $86.89   4.319%   $90.6428   $90.64   $90.65   $90.60  
  Purchase #5 $158.54   10.727%   $175.5466   $175.55   $175.55   $175.50  
  Purchase #6 $20.50   6.280%   $21.7874   $21.79   $21.80   $21.80  
  Purchase #7 $10.55   11.128%   $11.724   $11.72   $11.70   $11.70  
  7 purchase totals = $737.04       $794.1133   $794.12   $794.10   $794.00