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 $58.48   8.780%   $63.6145   $63.61   $63.60   $63.60  
  Purchase #2 $217.53   9.739%   $238.7152   $238.72   $238.70   $238.70  
  Purchase #3 $87.62   12.696%   $98.7442   $98.74   $98.75   $98.70  
  Purchase #4 $31.69   3.557%   $32.8172   $32.82   $32.80   $32.80  
  Purchase #5 $224.52   10.724%   $248.5975   $248.60   $248.60   $248.60  
  Purchase #6 $60.33   8.779%   $65.6264   $65.63   $65.65   $65.60  
  Purchase #7 $177.56   13.759%   $201.9905   $201.99   $202.00   $202.00  
  7 purchase totals = $857.73       $950.1055   $950.11   $950.10   $950.00