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 $95.76   7.478%   $102.9209   $102.92   $102.90   $102.90  
  Purchase #2 $211.97   7.397%   $227.6494   $227.65   $227.65   $227.60  
  Purchase #3 $221.34   9.731%   $242.8786   $242.88   $242.90   $242.90  
  Purchase #4 $146.78   8.685%   $159.5278   $159.53   $159.55   $159.50  
  Purchase #5 $65.48   3.145%   $67.5393   $67.54   $67.55   $67.50  
  Purchase #6 $234.28   7.695%   $252.3078   $252.31   $252.30   $252.30  
  Purchase #7 $40.59   6.156%   $43.0887   $43.09   $43.10   $43.10  
  7 purchase totals = $1,016.20       $1,095.9125   $1,095.92   $1,095.95   $1,095.80