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 $237.66   12.335%   $266.9754   $266.98   $267.00   $267.00  
  Purchase #2 $197.67   13.699%   $224.7488   $224.75   $224.75   $224.70  
  Purchase #3 $166.87   13.333%   $189.1188   $189.12   $189.10   $189.10  
  Purchase #4 $42.26   4.437%   $44.1351   $44.14   $44.15   $44.10  
  Purchase #5 $224.35   6.742%   $239.4757   $239.48   $239.50   $239.50  
  Purchase #6 $220.65   8.505%   $239.4163   $239.42   $239.40   $239.40  
  Purchase #7 $232.62   10.423%   $256.866   $256.87   $256.85   $256.90  
  7 purchase totals = $1,322.08       $1,460.7361   $1,460.76   $1,460.75   $1,460.70