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 $44.46   5.694%   $46.9916   $46.99   $47.00   $47.00  
  Purchase #2 $56.94   4.695%   $59.6133   $59.61   $59.60   $59.60  
  Purchase #3 $171.25   4.617%   $179.1566   $179.16   $179.15   $179.20  
  Purchase #4 $202.92   5.289%   $213.6524   $213.65   $213.65   $213.70  
  Purchase #5 $56.85   6.552%   $60.5748   $60.57   $60.55   $60.60  
  Purchase #6 $205.29   13.576%   $233.1602   $233.16   $233.15   $233.20  
  Purchase #7 $90.34   5.248%   $95.081   $95.08   $95.10   $95.10  
  7 purchase totals = $828.05       $888.2299   $888.22   $888.20   $888.40