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 $216.57   11.463%   $241.3954   $241.40   $241.40   $241.40  
  Purchase #2 $249.32   10.423%   $275.3066   $275.31   $275.30   $275.30  
  Purchase #3 $136.60   5.419%   $144.0024   $144.00   $144.00   $144.00  
  Purchase #4 $147.44   4.868%   $154.6174   $154.62   $154.60   $154.60  
  Purchase #5 $95.60   13.602%   $108.6035   $108.60   $108.60   $108.60  
  Purchase #6 $95.99   6.366%   $102.1007   $102.10   $102.10   $102.10  
  Purchase #7 $86.55   11.631%   $96.6166   $96.62   $96.60   $96.60  
  7 purchase totals = $1,028.07       $1,122.6426   $1,122.65   $1,122.60   $1,122.60