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 $241.67   8.799%   $262.9345   $262.93   $262.95   $262.90  
  Purchase #2 $240.33   9.156%   $262.3346   $262.33   $262.35   $262.30  
  Purchase #3 $53.60   9.819%   $58.863   $58.86   $58.85   $58.90  
  Purchase #4 $143.31   5.531%   $151.2365   $151.24   $151.25   $151.20  
  Purchase #5 $160.37   10.803%   $177.6948   $177.69   $177.70   $177.70  
  Purchase #6 $134.86   5.799%   $142.6805   $142.68   $142.70   $142.70  
  Purchase #7 $153.78   9.607%   $168.5536   $168.55   $168.55   $168.60  
  7 purchase totals = $1,127.92       $1,224.2975   $1,224.28   $1,224.35   $1,224.30