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 $232.70   5.507%   $245.5148   $245.51   $245.50   $245.50  
  Purchase #2 $85.77   11.534%   $95.6627   $95.66   $95.65   $95.70  
  Purchase #3 $108.46   5.324%   $114.2344   $114.23   $114.25   $114.20  
  Purchase #4 $155.36   8.759%   $168.968   $168.97   $168.95   $169.00  
  Purchase #5 $206.68   12.648%   $232.8209   $232.82   $232.80   $232.80  
  Purchase #6 $205.57   3.404%   $212.5676   $212.57   $212.55   $212.60  
  Purchase #7 $23.59   3.798%   $24.4859   $24.49   $24.50   $24.50  
  7 purchase totals = $1,018.13       $1,094.2543   $1,094.25   $1,094.20   $1,094.30