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 $223.77   9.143%   $244.2293   $244.23   $244.25   $244.20  
  Purchase #2 $58.57   3.619%   $60.6896   $60.69   $60.70   $60.70  
  Purchase #3 $84.28   5.340%   $88.7806   $88.78   $88.80   $88.80  
  Purchase #4 $240.44   7.444%   $258.3384   $258.34   $258.35   $258.30  
  Purchase #5 $207.34   8.853%   $225.6958   $225.70   $225.70   $225.70  
  Purchase #6 $49.62   3.394%   $51.3041   $51.30   $51.30   $51.30  
  Purchase #7 $23.31   4.774%   $24.4228   $24.42   $24.40   $24.40  
  7 purchase totals = $887.33       $953.4606   $953.46   $953.50   $953.40