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 $83.69   13.292%   $94.8141   $94.81   $94.80   $94.80  
  Purchase #2 $109.95   4.228%   $114.5987   $114.60   $114.60   $114.60  
  Purchase #3 $135.88   6.462%   $144.6606   $144.66   $144.65   $144.70  
  Purchase #4 $161.56   3.549%   $167.2938   $167.29   $167.30   $167.30  
  Purchase #5 $234.96   5.852%   $248.7099   $248.71   $248.70   $248.70  
  Purchase #6 $161.56   6.750%   $172.4653   $172.47   $172.45   $172.50  
  Purchase #7 $246.98   5.573%   $260.7442   $260.74   $260.75   $260.70  
  7 purchase totals = $1,134.58       $1,203.2866   $1,203.28   $1,203.25   $1,203.30