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 $178.57   10.703%   $197.6823   $197.68   $197.70   $197.70  
  Purchase #2 $112.79   11.115%   $125.3266   $125.33   $125.35   $125.30  
  Purchase #3 $159.95   10.726%   $177.1062   $177.11   $177.10   $177.10  
  Purchase #4 $41.73   8.756%   $45.3839   $45.38   $45.40   $45.40  
  Purchase #5 $207.75   6.371%   $220.9858   $220.99   $221.00   $221.00  
  Purchase #6 $246.68   5.573%   $260.4275   $260.43   $260.45   $260.40  
  Purchase #7 $82.27   12.117%   $92.2387   $92.24   $92.25   $92.20  
  7 purchase totals = $1,029.74       $1,119.1510   $1,119.16   $1,119.25   $1,119.10