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 $230.88   6.811%   $246.6052   $246.61   $246.60   $246.60  
  Purchase #2 $238.39   8.372%   $258.348   $258.35   $258.35   $258.30  
  Purchase #3 $108.74   7.781%   $117.2011   $117.20   $117.20   $117.20  
  Purchase #4 $65.56   6.275%   $69.6739   $69.67   $69.65   $69.70  
  Purchase #5 $161.88   11.620%   $180.6905   $180.69   $180.70   $180.70  
  Purchase #6 $114.77   5.435%   $121.0077   $121.01   $121.00   $121.00  
  Purchase #7 $196.81   7.545%   $211.6593   $211.66   $211.65   $211.70  
  7 purchase totals = $1,117.03       $1,205.1857   $1,205.19   $1,205.15   $1,205.20