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 $85.48   10.723%   $94.646   $94.65   $94.65   $94.60  
  Purchase #2 $129.42   3.216%   $133.5821   $133.58   $133.60   $133.60  
  Purchase #3 $191.99   5.785%   $203.0966   $203.10   $203.10   $203.10  
  Purchase #4 $70.88   12.366%   $79.645   $79.65   $79.65   $79.60  
  Purchase #5 $69.64   12.467%   $78.322   $78.32   $78.30   $78.30  
  Purchase #6 $245.61   8.361%   $266.1455   $266.15   $266.15   $266.10  
  Purchase #7 $177.49   11.403%   $197.7292   $197.73   $197.75   $197.70  
  7 purchase totals = $970.51       $1,053.1664   $1,053.18   $1,053.20   $1,053.00