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 $69.37   7.342%   $74.4631   $74.46   $74.45   $74.50  
  Purchase #2 $212.76   11.258%   $236.7125   $236.71   $236.70   $236.70  
  Purchase #3 $40.49   12.801%   $45.6731   $45.67   $45.65   $45.70  
  Purchase #4 $133.32   7.591%   $143.4403   $143.44   $143.45   $143.40  
  Purchase #5 $233.97   9.584%   $256.3937   $256.39   $256.40   $256.40  
  Purchase #6 $102.39   3.451%   $105.9235   $105.92   $105.90   $105.90  
  Purchase #7 $111.81   7.837%   $120.5725   $120.57   $120.55   $120.60  
  7 purchase totals = $904.11       $983.1787   $983.16   $983.10   $983.20