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 $102.99   10.791%   $114.1037   $114.10   $114.10   $114.10  
  Purchase #2 $36.48   6.139%   $38.7195   $38.72   $38.70   $38.70  
  Purchase #3 $220.51   7.116%   $236.2015   $236.20   $236.20   $236.20  
  Purchase #4 $198.41   12.769%   $223.745   $223.75   $223.75   $223.70  
  Purchase #5 $246.76   4.498%   $257.8593   $257.86   $257.85   $257.90  
  Purchase #6 $233.51   10.769%   $258.6567   $258.66   $258.65   $258.70  
  Purchase #7 $56.59   11.260%   $62.962   $62.96   $62.95   $63.00  
  7 purchase totals = $1,095.25       $1,192.2477   $1,192.25   $1,192.20   $1,192.30