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 $118.92   6.173%   $126.2609   $126.26   $126.25   $126.30  
  Purchase #2 $58.33   6.568%   $62.1611   $62.16   $62.15   $62.20  
  Purchase #3 $185.87   7.161%   $199.1802   $199.18   $199.20   $199.20  
  Purchase #4 $5.46   5.483%   $5.7594   $5.76   $5.75   $5.80  
  Purchase #5 $23.87   9.153%   $26.0548   $26.05   $26.05   $26.10  
  Purchase #6 $191.67   3.840%   $199.0301   $199.03   $199.05   $199.00  
  Purchase #7 $108.98   4.739%   $114.1446   $114.14   $114.15   $114.10  
  7 purchase totals = $693.10       $732.5911   $732.58   $732.60   $732.70