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 $59.94   5.135%   $63.0179   $63.02   $63.00   $63.00  
  Purchase #2 $233.81   12.835%   $263.8195   $263.82   $263.80   $263.80  
  Purchase #3 $158.30   9.315%   $173.0456   $173.05   $173.05   $173.00  
  Purchase #4 $36.50   13.618%   $41.4706   $41.47   $41.45   $41.50  
  Purchase #5 $223.78   6.379%   $238.0549   $238.05   $238.05   $238.10  
  Purchase #6 $208.56   13.422%   $236.5529   $236.55   $236.55   $236.60  
  Purchase #7 $166.60   9.346%   $182.1704   $182.17   $182.15   $182.20  
  7 purchase totals = $1,087.49       $1,198.1318   $1,198.13   $1,198.05   $1,198.20