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 $32.59   8.397%   $35.3266   $35.33   $35.35   $35.30  
  Purchase #2 $24.86   9.418%   $27.2013   $27.20   $27.20   $27.20  
  Purchase #3 $169.28   7.548%   $182.0573   $182.06   $182.05   $182.10  
  Purchase #4 $157.29   10.403%   $173.6529   $173.65   $173.65   $173.70  
  Purchase #5 $180.93   11.354%   $201.4728   $201.47   $201.45   $201.50  
  Purchase #6 $188.71   8.702%   $205.1315   $205.13   $205.15   $205.10  
  Purchase #7 $221.35   13.174%   $250.5106   $250.51   $250.50   $250.50  
  7 purchase totals = $975.01       $1,075.3530   $1,075.35   $1,075.35   $1,075.40