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 $107.45   6.621%   $114.5643   $114.56   $114.55   $114.60  
  Purchase #2 $163.55   3.803%   $169.7698   $169.77   $169.75   $169.80  
  Purchase #3 $147.68   9.374%   $161.5235   $161.52   $161.50   $161.50  
  Purchase #4 $230.96   7.458%   $248.185   $248.19   $248.20   $248.20  
  Purchase #5 $202.90   7.709%   $218.5416   $218.54   $218.55   $218.50  
  Purchase #6 $87.96   5.356%   $92.6711   $92.67   $92.65   $92.70  
  Purchase #7 $234.51   4.665%   $245.4499   $245.45   $245.45   $245.40  
  7 purchase totals = $1,175.01       $1,250.7052   $1,250.70   $1,250.65   $1,250.70