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 $209.44   11.364%   $233.2408   $233.24   $233.25   $233.20  
  Purchase #2 $196.99   12.513%   $221.6394   $221.64   $221.65   $221.60  
  Purchase #3 $220.94   9.317%   $241.525   $241.53   $241.55   $241.50  
  Purchase #4 $128.48   4.602%   $134.3926   $134.39   $134.40   $134.40  
  Purchase #5 $29.79   5.188%   $31.3355   $31.34   $31.35   $31.30  
  Purchase #6 $69.92   11.791%   $78.1643   $78.16   $78.15   $78.20  
  Purchase #7 $165.63   12.783%   $186.8025   $186.80   $186.80   $186.80  
  7 purchase totals = $1,021.19       $1,127.1001   $1,127.10   $1,127.15   $1,127.00