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 $58.68   13.651%   $66.6904   $66.69   $66.70   $66.70  
  Purchase #2 $202.77   5.387%   $213.6932   $213.69   $213.70   $213.70  
  Purchase #3 $220.83   4.143%   $229.979   $229.98   $230.00   $230.00  
  Purchase #4 $244.64   8.134%   $264.539   $264.54   $264.55   $264.50  
  Purchase #5 $229.69   5.415%   $242.1277   $242.13   $242.15   $242.10  
  Purchase #6 $191.30   13.791%   $217.6822   $217.68   $217.70   $217.70  
  Purchase #7 $212.49   8.287%   $230.099   $230.10   $230.10   $230.10  
  7 purchase totals = $1,360.40       $1,464.8105   $1,464.81   $1,464.90   $1,464.80