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 $84.96   12.107%   $95.2461   $95.25   $95.25   $95.20  
  Purchase #2 $114.54   10.649%   $126.7374   $126.74   $126.75   $126.70  
  Purchase #3 $152.61   10.693%   $168.9286   $168.93   $168.95   $168.90  
  Purchase #4 $69.77   3.809%   $72.4275   $72.43   $72.45   $72.40  
  Purchase #5 $64.52   4.503%   $67.4253   $67.43   $67.45   $67.40  
  Purchase #6 $51.87   8.157%   $56.101   $56.10   $56.10   $56.10  
  Purchase #7 $176.48   5.406%   $186.0205   $186.02   $186.00   $186.00  
  7 purchase totals = $714.75       $772.8864   $772.90   $772.95   $772.70