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 $241.80   8.231%   $261.7026   $261.70   $261.70   $261.70  
  Purchase #2 $223.82   7.834%   $241.3541   $241.35   $241.35   $241.40  
  Purchase #3 $89.40   6.366%   $95.0912   $95.09   $95.10   $95.10  
  Purchase #4 $49.29   7.601%   $53.0365   $53.04   $53.05   $53.00  
  Purchase #5 $117.97   7.435%   $126.7411   $126.74   $126.75   $126.70  
  Purchase #6 $22.92   10.851%   $25.407   $25.41   $25.40   $25.40  
  Purchase #7 $184.46   13.632%   $209.6056   $209.61   $209.60   $209.60  
  7 purchase totals = $929.66       $1,012.9381   $1,012.94   $1,012.95   $1,012.90