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 $192.29   5.231%   $202.3487   $202.35   $202.35   $202.30  
  Purchase #2 $24.27   10.330%   $26.7771   $26.78   $26.80   $26.80  
  Purchase #3 $76.67   6.129%   $81.3691   $81.37   $81.35   $81.40  
  Purchase #4 $223.48   9.335%   $244.3419   $244.34   $244.35   $244.30  
  Purchase #5 $217.79   13.607%   $247.4247   $247.42   $247.40   $247.40  
  Purchase #6 $182.37   12.831%   $205.7699   $205.77   $205.75   $205.80  
  Purchase #7 $217.49   4.768%   $227.8599   $227.86   $227.85   $227.90  
  7 purchase totals = $1,134.36       $1,235.8913   $1,235.89   $1,235.85   $1,235.90