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 $154.42   5.352%   $162.6846   $162.68   $162.70   $162.70  
  Purchase #2 $239.88   9.377%   $262.3735   $262.37   $262.35   $262.40  
  Purchase #3 $15.59   8.855%   $16.9705   $16.97   $16.95   $17.00  
  Purchase #4 $239.39   9.562%   $262.2805   $262.28   $262.30   $262.30  
  Purchase #5 $242.53   9.152%   $264.7263   $264.73   $264.75   $264.70  
  Purchase #6 $28.28   12.788%   $31.8964   $31.90   $31.90   $31.90  
  Purchase #7 $185.43   8.397%   $201.0006   $201.00   $201.00   $201.00  
  7 purchase totals = $1,105.52       $1,201.9324   $1,201.93   $1,201.95   $1,202.00