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 $87.61   9.622%   $96.0398   $96.04   $96.05   $96.00  
  Purchase #2 $205.26   13.861%   $233.7111   $233.71   $233.70   $233.70  
  Purchase #3 $234.41   8.482%   $254.2927   $254.29   $254.30   $254.30  
  Purchase #4 $106.87   10.500%   $118.0914   $118.09   $118.10   $118.10  
  Purchase #5 $20.90   8.712%   $22.7208   $22.72   $22.70   $22.70  
  Purchase #6 $85.66   9.235%   $93.5707   $93.57   $93.55   $93.60  
  Purchase #7 $167.50   5.549%   $176.7946   $176.79   $176.80   $176.80  
  7 purchase totals = $908.21       $995.2211   $995.21   $995.20   $995.20