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 $58.50   7.775%   $63.0484   $63.05   $63.05   $63.00  
  Purchase #2 $211.95   11.634%   $236.6083   $236.61   $236.60   $236.60  
  Purchase #3 $246.62   3.726%   $255.8091   $255.81   $255.80   $255.80  
  Purchase #4 $167.63   10.292%   $184.8825   $184.88   $184.90   $184.90  
  Purchase #5 $36.30   3.198%   $37.4609   $37.46   $37.45   $37.50  
  Purchase #6 $37.55   11.264%   $41.7796   $41.78   $41.80   $41.80  
  Purchase #7 $175.93   8.566%   $191.0002   $191.00   $191.00   $191.00  
  7 purchase totals = $934.48       $1,010.5890   $1,010.59   $1,010.60   $1,010.60