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 $56.85   10.194%   $62.6453   $62.65   $62.65   $62.60  
  Purchase #2 $33.31   9.437%   $36.4535   $36.45   $36.45   $36.50  
  Purchase #3 $176.63   11.394%   $196.7552   $196.76   $196.75   $196.80  
  Purchase #4 $5.33   6.697%   $5.687   $5.69   $5.70   $5.70  
  Purchase #5 $162.48   5.343%   $171.1613   $171.16   $171.15   $171.20  
  Purchase #6 $206.27   11.306%   $229.5909   $229.59   $229.60   $229.60  
  Purchase #7 $223.70   12.513%   $251.6916   $251.69   $251.70   $251.70  
  7 purchase totals = $864.57       $953.9848   $953.99   $954.00   $954.10