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 $234.62   11.684%   $262.033   $262.03   $262.05   $262.00  
  Purchase #2 $161.58   11.373%   $179.9565   $179.96   $179.95   $180.00  
  Purchase #3 $189.51   3.513%   $196.1675   $196.17   $196.15   $196.20  
  Purchase #4 $173.91   7.426%   $186.8246   $186.82   $186.80   $186.80  
  Purchase #5 $14.58   11.189%   $16.2114   $16.21   $16.20   $16.20  
  Purchase #6 $49.67   4.436%   $51.8734   $51.87   $51.85   $51.90  
  Purchase #7 $198.29   6.569%   $211.3157   $211.32   $211.30   $211.30  
  7 purchase totals = $1,022.16       $1,104.3821   $1,104.38   $1,104.30   $1,104.40