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 $102.62   8.512%   $111.355   $111.36   $111.35   $111.40  
  Purchase #2 $241.84   5.365%   $254.8147   $254.81   $254.80   $254.80  
  Purchase #3 $32.39   5.176%   $34.0665   $34.07   $34.05   $34.10  
  Purchase #4 $57.53   9.693%   $63.1064   $63.11   $63.10   $63.10  
  Purchase #5 $93.37   9.482%   $102.2233   $102.22   $102.20   $102.20  
  Purchase #6 $30.63   9.279%   $33.4722   $33.47   $33.45   $33.50  
  Purchase #7 $250.55   10.355%   $276.4945   $276.49   $276.50   $276.50  
  7 purchase totals = $808.93       $875.5326   $875.53   $875.45   $875.60