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 $239.49   5.742%   $253.2415   $253.24   $253.25   $253.20  
  Purchase #2 $41.93   3.351%   $43.3351   $43.34   $43.35   $43.30  
  Purchase #3 $214.48   10.372%   $236.7259   $236.73   $236.75   $236.70  
  Purchase #4 $58.52   8.301%   $63.3777   $63.38   $63.40   $63.40  
  Purchase #5 $201.48   11.687%   $225.027   $225.03   $225.05   $225.00  
  Purchase #6 $146.61   9.372%   $160.3503   $160.35   $160.35   $160.40  
  Purchase #7 $134.59   8.470%   $145.9898   $145.99   $146.00   $146.00  
  7 purchase totals = $1,037.10       $1,128.0473   $1,128.06   $1,128.15   $1,128.00