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 $202.53   4.505%   $211.654   $211.65   $211.65   $211.70  
  Purchase #2 $180.29   9.305%   $197.066   $197.07   $197.05   $197.10  
  Purchase #3 $221.38   5.509%   $233.5758   $233.58   $233.60   $233.60  
  Purchase #4 $52.98   12.486%   $59.5951   $59.60   $59.60   $59.60  
  Purchase #5 $53.88   12.836%   $60.796   $60.80   $60.80   $60.80  
  Purchase #6 $117.51   7.802%   $126.6781   $126.68   $126.70   $126.70  
  Purchase #7 $127.29   7.818%   $137.2415   $137.24   $137.25   $137.20  
  7 purchase totals = $955.86       $1,026.6065   $1,026.62   $1,026.65   $1,026.70