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 $87.42   7.589%   $94.0543   $94.05   $94.05   $94.10  
  Purchase #2 $52.41   4.504%   $54.7705   $54.77   $54.75   $54.80  
  Purchase #3 $101.74   7.445%   $109.3145   $109.31   $109.30   $109.30  
  Purchase #4 $242.96   7.670%   $261.595   $261.60   $261.60   $261.60  
  Purchase #5 $239.37   5.677%   $252.959   $252.96   $252.95   $253.00  
  Purchase #6 $181.66   6.155%   $192.8412   $192.84   $192.85   $192.80  
  Purchase #7 $78.35   10.435%   $86.5258   $86.53   $86.55   $86.50  
  7 purchase totals = $983.91       $1,052.0603   $1,052.06   $1,052.05   $1,052.10