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 $117.62   7.141%   $126.0192   $126.02   $126.00   $126.00  
  Purchase #2 $175.51   10.450%   $193.8508   $193.85   $193.85   $193.90  
  Purchase #3 $150.94   3.747%   $156.5957   $156.60   $156.60   $156.60  
  Purchase #4 $47.79   4.386%   $49.8861   $49.89   $49.90   $49.90  
  Purchase #5 $100.88   6.744%   $107.6833   $107.68   $107.70   $107.70  
  Purchase #6 $239.87   5.609%   $253.3243   $253.32   $253.30   $253.30  
  Purchase #7 $248.55   6.157%   $263.8532   $263.85   $263.85   $263.90  
  7 purchase totals = $1,081.16       $1,151.2126   $1,151.21   $1,151.20   $1,151.30