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 $62.48   10.513%   $69.0485   $69.05   $69.05   $69.00  
  Purchase #2 $230.99   6.792%   $246.6788   $246.68   $246.70   $246.70  
  Purchase #3 $162.53   8.338%   $176.0818   $176.08   $176.10   $176.10  
  Purchase #4 $189.48   4.479%   $197.9668   $197.97   $197.95   $198.00  
  Purchase #5 $11.98   3.325%   $12.3783   $12.38   $12.40   $12.40  
  Purchase #6 $41.68   12.271%   $46.7946   $46.79   $46.80   $46.80  
  Purchase #7 $184.62   12.151%   $207.0532   $207.05   $207.05   $207.10  
  7 purchase totals = $883.76       $956.0020   $956.00   $956.05   $956.10