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 $193.53   3.870%   $201.0196   $201.02   $201.00   $201.00  
  Purchase #2 $194.91   12.360%   $219.0009   $219.00   $219.00   $219.00  
  Purchase #3 $15.82   3.533%   $16.3789   $16.38   $16.40   $16.40  
  Purchase #4 $248.40   7.709%   $267.5492   $267.55   $267.55   $267.50  
  Purchase #5 $218.54   13.850%   $248.8078   $248.81   $248.80   $248.80  
  Purchase #6 $132.92   8.804%   $144.6223   $144.62   $144.60   $144.60  
  Purchase #7 $46.56   7.324%   $49.9701   $49.97   $49.95   $50.00  
  7 purchase totals = $1,050.68       $1,147.3488   $1,147.35   $1,147.30   $1,147.30