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 $62.85   5.789%   $66.4884   $66.49   $66.50   $66.50  
  Purchase #2 $87.80   9.872%   $96.4676   $96.47   $96.45   $96.50  
  Purchase #3 $188.73   3.656%   $195.63   $195.63   $195.65   $195.60  
  Purchase #4 $194.67   8.783%   $211.7679   $211.77   $211.75   $211.80  
  Purchase #5 $169.93   3.637%   $176.1104   $176.11   $176.10   $176.10  
  Purchase #6 $127.69   5.627%   $134.8751   $134.88   $134.90   $134.90  
  Purchase #7 $112.74   13.590%   $128.0614   $128.06   $128.05   $128.10  
  7 purchase totals = $944.41       $1,009.4008   $1,009.41   $1,009.40   $1,009.50