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 $149.97   7.660%   $161.4577   $161.46   $161.45   $161.50  
  Purchase #2 $225.83   6.807%   $241.2022   $241.20   $241.20   $241.20  
  Purchase #3 $202.84   4.364%   $211.6919   $211.69   $211.70   $211.70  
  Purchase #4 $74.99   4.795%   $78.5858   $78.59   $78.60   $78.60  
  Purchase #5 $206.34   7.417%   $221.6442   $221.64   $221.65   $221.60  
  Purchase #6 $141.69   3.147%   $146.149   $146.15   $146.15   $146.10  
  Purchase #7 $22.36   3.739%   $23.196   $23.20   $23.20   $23.20  
  7 purchase totals = $1,024.02       $1,083.9268   $1,083.93   $1,083.95   $1,083.90