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 $69.25   7.490%   $74.4368   $74.44   $74.45   $74.40  
  Purchase #2 $59.52   13.588%   $67.6076   $67.61   $67.60   $67.60  
  Purchase #3 $187.73   13.801%   $213.6386   $213.64   $213.65   $213.60  
  Purchase #4 $123.37   8.273%   $133.5764   $133.58   $133.60   $133.60  
  Purchase #5 $15.76   11.263%   $17.535   $17.54   $17.55   $17.50  
  Purchase #6 $47.62   12.439%   $53.5435   $53.54   $53.55   $53.50  
  Purchase #7 $197.47   8.157%   $213.5776   $213.58   $213.60   $213.60  
  7 purchase totals = $700.72       $773.9155   $773.93   $774.00   $773.80