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 $183.34   6.140%   $194.5971   $194.60   $194.60   $194.60  
  Purchase #2 $170.56   4.746%   $178.6548   $178.65   $178.65   $178.70  
  Purchase #3 $213.58   4.523%   $223.2402   $223.24   $223.25   $223.20  
  Purchase #4 $26.30   5.768%   $27.817   $27.82   $27.80   $27.80  
  Purchase #5 $179.64   8.578%   $195.0495   $195.05   $195.05   $195.00  
  Purchase #6 $38.54   8.467%   $41.8032   $41.80   $41.80   $41.80  
  Purchase #7 $175.25   4.688%   $183.4657   $183.47   $183.45   $183.50  
  7 purchase totals = $987.21       $1,044.6275   $1,044.63   $1,044.60   $1,044.60