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 $84.48   12.488%   $95.0299   $95.03   $95.05   $95.00  
  Purchase #2 $37.84   13.467%   $42.9359   $42.94   $42.95   $42.90  
  Purchase #3 $54.64   7.477%   $58.7254   $58.73   $58.75   $58.70  
  Purchase #4 $189.78   11.519%   $211.6408   $211.64   $211.65   $211.60  
  Purchase #5 $146.26   12.476%   $164.5074   $164.51   $164.50   $164.50  
  Purchase #6 $6.38   4.379%   $6.6594   $6.66   $6.65   $6.70  
  Purchase #7 $182.80   11.488%   $203.8001   $203.80   $203.80   $203.80  
  7 purchase totals = $702.18       $783.2989   $783.31   $783.35   $783.20