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 $163.38   8.120%   $176.6465   $176.65   $176.65   $176.60  
  Purchase #2 $250.31   7.388%   $268.8029   $268.80   $268.80   $268.80  
  Purchase #3 $184.70   7.381%   $198.3327   $198.33   $198.35   $198.30  
  Purchase #4 $209.94   6.789%   $224.1928   $224.19   $224.20   $224.20  
  Purchase #5 $14.64   11.688%   $16.3511   $16.35   $16.35   $16.40  
  Purchase #6 $44.82   5.797%   $47.4182   $47.42   $47.40   $47.40  
  Purchase #7 $124.93   8.476%   $135.5191   $135.52   $135.50   $135.50  
  7 purchase totals = $992.72       $1,067.2633   $1,067.26   $1,067.25   $1,067.20