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 $30.62   7.645%   $32.9609   $32.96   $32.95   $33.00  
  Purchase #2 $234.56   7.307%   $251.6993   $251.70   $251.70   $251.70  
  Purchase #3 $112.70   12.243%   $126.4979   $126.50   $126.50   $126.50  
  Purchase #4 $153.45   6.181%   $162.9347   $162.93   $162.95   $162.90  
  Purchase #5 $115.33   12.456%   $129.6955   $129.70   $129.70   $129.70  
  Purchase #6 $230.28   5.371%   $242.6483   $242.65   $242.65   $242.60  
  Purchase #7 $154.75   4.691%   $162.0093   $162.01   $162.00   $162.00  
  7 purchase totals = $1,031.69       $1,108.4459   $1,108.45   $1,108.45   $1,108.40