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 $63.83   6.624%   $68.0581   $68.06   $68.05   $68.10  
  Purchase #2 $242.42   8.574%   $263.2051   $263.21   $263.20   $263.20  
  Purchase #3 $52.59   10.490%   $58.1067   $58.11   $58.10   $58.10  
  Purchase #4 $64.71   5.244%   $68.1034   $68.10   $68.10   $68.10  
  Purchase #5 $144.45   13.605%   $164.1024   $164.10   $164.10   $164.10  
  Purchase #6 $171.57   13.680%   $195.0408   $195.04   $195.05   $195.00  
  Purchase #7 $185.92   10.638%   $205.6982   $205.70   $205.70   $205.70  
  7 purchase totals = $925.49       $1,022.3147   $1,022.32   $1,022.30   $1,022.30