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 $31.95   9.383%   $34.9479   $34.95   $34.95   $34.90  
  Purchase #2 $239.83   12.523%   $269.8639   $269.86   $269.85   $269.90  
  Purchase #3 $81.36   4.480%   $85.0049   $85.00   $85.00   $85.00  
  Purchase #4 $149.88   6.593%   $159.7616   $159.76   $159.75   $159.80  
  Purchase #5 $237.88   12.256%   $267.0346   $267.03   $267.05   $267.00  
  Purchase #6 $145.48   10.637%   $160.9547   $160.95   $160.95   $161.00  
  Purchase #7 $180.31   10.579%   $199.385   $199.39   $199.40   $199.40  
  7 purchase totals = $1,066.69       $1,176.9526   $1,176.94   $1,176.95   $1,177.00