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 $244.82   6.702%   $261.2278   $261.23   $261.25   $261.20  
  Purchase #2 $204.45   9.404%   $223.6765   $223.68   $223.70   $223.70  
  Purchase #3 $168.82   4.442%   $176.319   $176.32   $176.30   $176.30  
  Purchase #4 $113.31   3.734%   $117.541   $117.54   $117.55   $117.50  
  Purchase #5 $114.76   4.532%   $119.9609   $119.96   $119.95   $120.00  
  Purchase #6 $60.47   4.143%   $62.9753   $62.98   $63.00   $63.00  
  Purchase #7 $161.58   5.450%   $170.3861   $170.39   $170.40   $170.40  
  7 purchase totals = $1,068.21       $1,132.0866   $1,132.10   $1,132.15   $1,132.10