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 $239.63   9.427%   $262.2199   $262.22   $262.20   $262.20  
  Purchase #2 $56.77   8.286%   $61.474   $61.47   $61.45   $61.50  
  Purchase #3 $45.71   7.464%   $49.1218   $49.12   $49.10   $49.10  
  Purchase #4 $108.78   4.775%   $113.9742   $113.97   $113.95   $114.00  
  Purchase #5 $203.62   11.217%   $226.4601   $226.46   $226.45   $226.50  
  Purchase #6 $124.66   12.106%   $139.7513   $139.75   $139.75   $139.80  
  Purchase #7 $173.38   4.716%   $181.5566   $181.56   $181.55   $181.60  
  7 purchase totals = $952.55       $1,034.5579   $1,034.55   $1,034.45   $1,034.70