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 $104.59   11.626%   $116.7496   $116.75   $116.75   $116.70  
  Purchase #2 $228.29   6.565%   $243.2772   $243.28   $243.30   $243.30  
  Purchase #3 $35.26   13.273%   $39.9401   $39.94   $39.95   $39.90  
  Purchase #4 $167.96   3.686%   $174.151   $174.15   $174.15   $174.20  
  Purchase #5 $77.89   6.558%   $82.998   $83.00   $83.00   $83.00  
  Purchase #6 $242.71   9.489%   $265.7408   $265.74   $265.75   $265.70  
  Purchase #7 $183.81   13.693%   $208.9791   $208.98   $209.00   $209.00  
  7 purchase totals = $1,040.51       $1,131.8358   $1,131.84   $1,131.90   $1,131.80