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 $233.63   7.496%   $251.1429   $251.14   $251.15   $251.10  
  Purchase #2 $237.92   8.676%   $258.5619   $258.56   $258.55   $258.60  
  Purchase #3 $213.70   6.192%   $226.9323   $226.93   $226.95   $226.90  
  Purchase #4 $70.45   8.613%   $76.5179   $76.52   $76.50   $76.50  
  Purchase #5 $165.49   5.303%   $174.2659   $174.27   $174.25   $174.30  
  Purchase #6 $24.92   6.431%   $26.5226   $26.52   $26.50   $26.50  
  Purchase #7 $213.75   7.853%   $230.5358   $230.54   $230.55   $230.50  
  7 purchase totals = $1,159.86       $1,244.4793   $1,244.48   $1,244.45   $1,244.40