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 $87.75   8.477%   $95.1886   $95.19   $95.20   $95.20  
  Purchase #2 $246.90   12.432%   $277.5946   $277.59   $277.60   $277.60  
  Purchase #3 $106.77   9.592%   $117.0114   $117.01   $117.00   $117.00  
  Purchase #4 $27.63   9.119%   $30.1496   $30.15   $30.15   $30.10  
  Purchase #5 $224.32   12.409%   $252.1559   $252.16   $252.15   $252.20  
  Purchase #6 $26.60   3.134%   $27.4336   $27.43   $27.45   $27.40  
  Purchase #7 $146.94   5.563%   $155.1143   $155.11   $155.10   $155.10  
  7 purchase totals = $866.91       $954.6480   $954.64   $954.65   $954.60