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 $197.83   8.477%   $214.6   $214.60   $214.60   $214.60  
  Purchase #2 $176.41   12.273%   $198.0608   $198.06   $198.05   $198.10  
  Purchase #3 $192.89   5.449%   $203.4006   $203.40   $203.40   $203.40  
  Purchase #4 $244.67   3.635%   $253.5638   $253.56   $253.55   $253.60  
  Purchase #5 $56.77   8.399%   $61.5381   $61.54   $61.55   $61.50  
  Purchase #6 $234.95   13.621%   $266.9525   $266.95   $266.95   $267.00  
  Purchase #7 $237.33   9.111%   $258.9531   $258.95   $258.95   $259.00  
  7 purchase totals = $1,340.85       $1,457.0689   $1,457.06   $1,457.05   $1,457.20