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 $233.66   8.576%   $253.6987   $253.70   $253.70   $253.70  
  Purchase #2 $88.88   6.158%   $94.3532   $94.35   $94.35   $94.40  
  Purchase #3 $108.54   9.671%   $119.0369   $119.04   $119.05   $119.00  
  Purchase #4 $216.66   3.489%   $224.2193   $224.22   $224.20   $224.20  
  Purchase #5 $186.26   5.653%   $196.7893   $196.79   $196.80   $196.80  
  Purchase #6 $180.39   13.220%   $204.2376   $204.24   $204.25   $204.20  
  Purchase #7 $241.30   12.670%   $271.8727   $271.87   $271.85   $271.90  
  7 purchase totals = $1,255.69       $1,364.2077   $1,364.21   $1,364.20   $1,364.20