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 $241.74   8.520%   $262.3362   $262.34   $262.35   $262.30  
  Purchase #2 $96.87   8.390%   $104.9974   $105.00   $105.00   $105.00  
  Purchase #3 $134.72   6.781%   $143.8554   $143.86   $143.85   $143.90  
  Purchase #4 $171.87   12.143%   $192.7402   $192.74   $192.75   $192.70  
  Purchase #5 $155.61   11.609%   $173.6748   $173.67   $173.65   $173.70  
  Purchase #6 $78.85   6.216%   $83.7513   $83.75   $83.75   $83.80  
  Purchase #7 $205.28   4.464%   $214.4437   $214.44   $214.45   $214.40  
  7 purchase totals = $1,084.94       $1,175.7990   $1,175.80   $1,175.80   $1,175.80