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 $85.84   11.466%   $95.6824   $95.68   $95.70   $95.70  
  Purchase #2 $163.81   6.604%   $174.628   $174.63   $174.65   $174.60  
  Purchase #3 $113.26   7.729%   $122.0139   $122.01   $122.00   $122.00  
  Purchase #4 $176.86   3.250%   $182.608   $182.61   $182.60   $182.60  
  Purchase #5 $35.81   13.830%   $40.7625   $40.76   $40.75   $40.80  
  Purchase #6 $214.39   9.761%   $235.3166   $235.32   $235.30   $235.30  
  Purchase #7 $247.90   9.592%   $271.6786   $271.68   $271.70   $271.70  
  7 purchase totals = $1,037.87       $1,122.6900   $1,122.69   $1,122.70   $1,122.70