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 $196.64   13.274%   $222.742   $222.74   $222.75   $222.70  
  Purchase #2 $202.38   3.682%   $209.8316   $209.83   $209.85   $209.80  
  Purchase #3 $245.98   8.602%   $267.1392   $267.14   $267.15   $267.10  
  Purchase #4 $191.45   11.285%   $213.0551   $213.06   $213.05   $213.10  
  Purchase #5 $211.80   10.447%   $233.9267   $233.93   $233.95   $233.90  
  Purchase #6 $209.87   9.765%   $230.3638   $230.36   $230.35   $230.40  
  Purchase #7 $86.40   5.568%   $91.2108   $91.21   $91.20   $91.20  
  7 purchase totals = $1,344.52       $1,468.2692   $1,468.27   $1,468.30   $1,468.20