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 $63.65   8.708%   $69.1926   $69.19   $69.20   $69.20  
  Purchase #2 $131.64   7.783%   $141.8855   $141.89   $141.90   $141.90  
  Purchase #3 $200.72   10.442%   $221.6792   $221.68   $221.70   $221.70  
  Purchase #4 $199.54   5.466%   $210.4469   $210.45   $210.45   $210.40  
  Purchase #5 $202.33   7.684%   $217.877   $217.88   $217.90   $217.90  
  Purchase #6 $182.25   9.866%   $200.2308   $200.23   $200.25   $200.20  
  Purchase #7 $181.61   5.268%   $191.1772   $191.18   $191.20   $191.20  
  7 purchase totals = $1,161.74       $1,252.4892   $1,252.50   $1,252.60   $1,252.50