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 $233.62   8.592%   $253.6926   $253.69   $253.70   $253.70  
  Purchase #2 $231.65   13.201%   $262.2301   $262.23   $262.25   $262.20  
  Purchase #3 $49.60   13.263%   $56.1784   $56.18   $56.20   $56.20  
  Purchase #4 $88.94   6.361%   $94.5975   $94.60   $94.60   $94.60  
  Purchase #5 $204.48   4.331%   $213.336   $213.34   $213.35   $213.30  
  Purchase #6 $176.45   3.404%   $182.4564   $182.46   $182.45   $182.50  
  Purchase #7 $22.66   9.484%   $24.8091   $24.81   $24.80   $24.80  
  7 purchase totals = $1,007.40       $1,087.3001   $1,087.31   $1,087.35   $1,087.30