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 $215.73   5.187%   $226.9199   $226.92   $226.90   $226.90  
  Purchase #2 $30.33   10.314%   $33.4582   $33.46   $33.45   $33.50  
  Purchase #3 $93.72   9.810%   $102.9139   $102.91   $102.90   $102.90  
  Purchase #4 $173.78   11.462%   $193.6987   $193.70   $193.70   $193.70  
  Purchase #5 $216.53   4.787%   $226.8953   $226.90   $226.90   $226.90  
  Purchase #6 $51.58   5.717%   $54.5288   $54.53   $54.55   $54.50  
  Purchase #7 $184.29   13.167%   $208.5555   $208.56   $208.55   $208.60  
  7 purchase totals = $965.96       $1,046.9703   $1,046.98   $1,046.95   $1,047.00