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 $216.26   3.699%   $224.2595   $224.26   $224.25   $224.30  
  Purchase #2 $73.90   4.364%   $77.125   $77.13   $77.15   $77.10  
  Purchase #3 $89.82   11.315%   $99.9831   $99.98   $100.00   $100.00  
  Purchase #4 $198.45   4.751%   $207.8784   $207.88   $207.90   $207.90  
  Purchase #5 $221.66   12.106%   $248.4942   $248.49   $248.50   $248.50  
  Purchase #6 $187.57   11.600%   $209.3281   $209.33   $209.35   $209.30  
  Purchase #7 $174.97   8.699%   $190.1906   $190.19   $190.20   $190.20  
  7 purchase totals = $1,162.63       $1,257.2589   $1,257.26   $1,257.35   $1,257.30