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 $114.83   4.342%   $119.8159   $119.82   $119.80   $119.80  
  Purchase #2 $168.82   9.367%   $184.6334   $184.63   $184.65   $184.60  
  Purchase #3 $22.95   12.262%   $25.7641   $25.76   $25.75   $25.80  
  Purchase #4 $238.59   8.661%   $259.2543   $259.25   $259.25   $259.30  
  Purchase #5 $85.63   9.361%   $93.6458   $93.65   $93.65   $93.60  
  Purchase #6 $183.77   5.153%   $193.2397   $193.24   $193.25   $193.20  
  Purchase #7 $167.38   5.156%   $176.0101   $176.01   $176.00   $176.00  
  7 purchase totals = $981.97       $1,052.3633   $1,052.36   $1,052.35   $1,052.30