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 $56.83   10.728%   $62.9267   $62.93   $62.95   $62.90  
  Purchase #2 $149.68   11.364%   $166.6896   $166.69   $166.70   $166.70  
  Purchase #3 $232.49   7.167%   $249.1526   $249.15   $249.15   $249.20  
  Purchase #4 $152.73   9.825%   $167.7357   $167.74   $167.75   $167.70  
  Purchase #5 $58.36   4.130%   $60.7703   $60.77   $60.75   $60.80  
  Purchase #6 $158.36   3.497%   $163.8978   $163.90   $163.90   $163.90  
  Purchase #7 $201.34   11.675%   $224.8464   $224.85   $224.85   $224.80  
  7 purchase totals = $1,009.79       $1,096.0191   $1,096.03   $1,096.05   $1,096.00