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 $45.95   3.608%   $47.6079   $47.61   $47.60   $47.60  
  Purchase #2 $117.34   6.781%   $125.2968   $125.30   $125.30   $125.30  
  Purchase #3 $173.65   5.225%   $182.7232   $182.72   $182.70   $182.70  
  Purchase #4 $232.89   6.769%   $248.6543   $248.65   $248.65   $248.70  
  Purchase #5 $216.88   7.445%   $233.0267   $233.03   $233.05   $233.00  
  Purchase #6 $237.35   7.198%   $254.4345   $254.43   $254.45   $254.40  
  Purchase #7 $191.28   5.709%   $202.2002   $202.20   $202.20   $202.20  
  7 purchase totals = $1,215.34       $1,293.9436   $1,293.94   $1,293.95   $1,293.90