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 $85.57   10.574%   $94.6182   $94.62   $94.60   $94.60  
  Purchase #2 $131.35   10.397%   $145.0065   $145.01   $145.00   $145.00  
  Purchase #3 $170.39   5.748%   $180.184   $180.18   $180.20   $180.20  
  Purchase #4 $187.56   4.679%   $196.3359   $196.34   $196.35   $196.30  
  Purchase #5 $36.86   5.298%   $38.8128   $38.81   $38.80   $38.80  
  Purchase #6 $242.75   3.653%   $251.6177   $251.62   $251.60   $251.60  
  Purchase #7 $107.88   9.409%   $118.0304   $118.03   $118.05   $118.00  
  7 purchase totals = $962.36       $1,024.6055   $1,024.61   $1,024.60   $1,024.50