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 $242.97   10.270%   $267.923   $267.92   $267.90   $267.90  
  Purchase #2 $237.84   6.619%   $253.5826   $253.58   $253.60   $253.60  
  Purchase #3 $44.37   3.697%   $46.0104   $46.01   $46.00   $46.00  
  Purchase #4 $94.46   12.756%   $106.5093   $106.51   $106.50   $106.50  
  Purchase #5 $146.64   3.509%   $151.7856   $151.79   $151.80   $151.80  
  Purchase #6 $229.33   5.610%   $242.1954   $242.20   $242.20   $242.20  
  Purchase #7 $25.46   6.173%   $27.0316   $27.03   $27.05   $27.00  
  7 purchase totals = $1,021.07       $1,095.0379   $1,095.04   $1,095.05   $1,095.00