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 $63.48   8.873%   $69.1126   $69.11   $69.10   $69.10  
  Purchase #2 $68.72   7.715%   $74.0217   $74.02   $74.00   $74.00  
  Purchase #3 $216.72   7.515%   $233.0065   $233.01   $233.00   $233.00  
  Purchase #4 $90.64   5.844%   $95.937   $95.94   $95.95   $95.90  
  Purchase #5 $15.60   11.752%   $17.4333   $17.43   $17.45   $17.40  
  Purchase #6 $95.62   8.522%   $103.7687   $103.77   $103.75   $103.80  
  Purchase #7 $181.88   12.583%   $204.766   $204.77   $204.75   $204.80  
  7 purchase totals = $732.66       $798.0458   $798.05   $798.00   $798.00