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 $29.58   13.408%   $33.5461   $33.55   $33.55   $33.50  
  Purchase #2 $173.41   12.658%   $195.3602   $195.36   $195.35   $195.40  
  Purchase #3 $142.56   13.346%   $161.5861   $161.59   $161.60   $161.60  
  Purchase #4 $75.44   4.132%   $78.5572   $78.56   $78.55   $78.60  
  Purchase #5 $244.92   6.586%   $261.0504   $261.05   $261.05   $261.10  
  Purchase #6 $182.47   6.590%   $194.4948   $194.49   $194.50   $194.50  
  Purchase #7 $171.90   5.677%   $181.6588   $181.66   $181.65   $181.70  
  7 purchase totals = $1,020.28       $1,106.2536   $1,106.26   $1,106.25   $1,106.40