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 $171.61   6.597%   $182.9311   $182.93   $182.95   $182.90  
  Purchase #2 $206.66   13.148%   $233.8317   $233.83   $233.85   $233.80  
  Purchase #3 $167.34   11.843%   $187.1581   $187.16   $187.15   $187.20  
  Purchase #4 $103.87   10.225%   $114.4907   $114.49   $114.50   $114.50  
  Purchase #5 $169.51   3.703%   $175.787   $175.79   $175.80   $175.80  
  Purchase #6 $236.46   3.363%   $244.4121   $244.41   $244.40   $244.40  
  Purchase #7 $208.57   6.793%   $222.7382   $222.74   $222.75   $222.70  
  7 purchase totals = $1,264.02       $1,361.3489   $1,361.35   $1,361.40   $1,361.30