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 $54.64   13.786%   $62.1727   $62.17   $62.15   $62.20  
  Purchase #2 $177.34   11.652%   $198.0037   $198.00   $198.00   $198.00  
  Purchase #3 $184.85   9.410%   $202.2444   $202.24   $202.25   $202.20  
  Purchase #4 $119.87   12.677%   $135.0659   $135.07   $135.05   $135.10  
  Purchase #5 $220.66   10.355%   $243.5093   $243.51   $243.50   $243.50  
  Purchase #6 $10.35   13.311%   $11.7277   $11.73   $11.75   $11.70  
  Purchase #7 $198.71   9.569%   $217.7246   $217.72   $217.70   $217.70  
  7 purchase totals = $966.42       $1,070.4483   $1,070.44   $1,070.40   $1,070.40