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 $247.59   13.735%   $281.5965   $281.60   $281.60   $281.60  
  Purchase #2 $101.75   4.157%   $105.9797   $105.98   $106.00   $106.00  
  Purchase #3 $56.31   4.761%   $58.9909   $58.99   $59.00   $59.00  
  Purchase #4 $204.78   3.338%   $211.6156   $211.62   $211.60   $211.60  
  Purchase #5 $10.26   8.490%   $11.1311   $11.13   $11.15   $11.10  
  Purchase #6 $217.97   6.661%   $232.489   $232.49   $232.50   $232.50  
  Purchase #7 $205.36   8.189%   $222.1769   $222.18   $222.20   $222.20  
  7 purchase totals = $1,044.02       $1,123.9797   $1,123.99   $1,124.05   $1,124.00