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 $113.95   8.568%   $123.7132   $123.71   $123.70   $123.70  
  Purchase #2 $202.38   5.740%   $213.9966   $214.00   $214.00   $214.00  
  Purchase #3 $159.90   9.322%   $174.8059   $174.81   $174.80   $174.80  
  Purchase #4 $203.88   4.601%   $213.2605   $213.26   $213.25   $213.30  
  Purchase #5 $200.69   8.383%   $217.5138   $217.51   $217.50   $217.50  
  Purchase #6 $154.30   8.613%   $167.5899   $167.59   $167.60   $167.60  
  Purchase #7 $191.80   3.167%   $197.8743   $197.87   $197.85   $197.90  
  7 purchase totals = $1,226.90       $1,308.7542   $1,308.75   $1,308.70   $1,308.80