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 $88.55   11.441%   $98.681   $98.68   $98.70   $98.70  
  Purchase #2 $176.42   5.691%   $186.4601   $186.46   $186.45   $186.50  
  Purchase #3 $86.73   9.521%   $94.9876   $94.99   $95.00   $95.00  
  Purchase #4 $163.97   3.423%   $169.5827   $169.58   $169.60   $169.60  
  Purchase #5 $32.96   7.501%   $35.4323   $35.43   $35.45   $35.40  
  Purchase #6 $240.32   8.411%   $260.5333   $260.53   $260.55   $260.50  
  Purchase #7 $195.48   3.810%   $202.9278   $202.93   $202.95   $202.90  
  7 purchase totals = $984.43       $1,048.6048   $1,048.60   $1,048.70   $1,048.60