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 $90.49   5.578%   $95.5375   $95.54   $95.55   $95.50  
  Purchase #2 $41.65   9.125%   $45.4506   $45.45   $45.45   $45.50  
  Purchase #3 $85.39   12.703%   $96.2371   $96.24   $96.25   $96.20  
  Purchase #4 $220.58   11.257%   $245.4107   $245.41   $245.40   $245.40  
  Purchase #5 $193.48   5.180%   $203.5023   $203.50   $203.50   $203.50  
  Purchase #6 $164.25   5.553%   $173.3708   $173.37   $173.35   $173.40  
  Purchase #7 $232.90   11.395%   $259.439   $259.44   $259.45   $259.40  
  7 purchase totals = $1,028.74       $1,118.9480   $1,118.95   $1,118.95   $1,118.90