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 $194.74   8.838%   $211.9511   $211.95   $211.95   $212.00  
  Purchase #2 $114.48   6.548%   $121.9762   $121.98   $122.00   $122.00  
  Purchase #3 $234.74   8.871%   $255.5638   $255.56   $255.55   $255.60  
  Purchase #4 $163.74   9.309%   $178.9826   $178.98   $179.00   $179.00  
  Purchase #5 $183.28   6.576%   $195.3325   $195.33   $195.35   $195.30  
  Purchase #6 $85.49   8.328%   $92.6096   $92.61   $92.60   $92.60  
  Purchase #7 $37.31   5.590%   $39.3956   $39.40   $39.40   $39.40  
  7 purchase totals = $1,013.78       $1,095.8114   $1,095.81   $1,095.85   $1,095.90