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 $244.49   10.120%   $269.2324   $269.23   $269.25   $269.20  
  Purchase #2 $94.95   12.584%   $106.8985   $106.90   $106.90   $106.90  
  Purchase #3 $69.64   10.265%   $76.7885   $76.79   $76.80   $76.80  
  Purchase #4 $92.69   10.329%   $102.264   $102.26   $102.25   $102.30  
  Purchase #5 $131.66   3.320%   $136.0311   $136.03   $136.05   $136.00  
  Purchase #6 $23.87   11.372%   $26.5845   $26.58   $26.60   $26.60  
  Purchase #7 $38.96   13.494%   $44.2173   $44.22   $44.20   $44.20  
  7 purchase totals = $696.26       $762.0163   $762.01   $762.05   $762.00