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 $168.69   5.676%   $178.2648   $178.26   $178.25   $178.30  
  Purchase #2 $244.37   6.743%   $260.8479   $260.85   $260.85   $260.80  
  Purchase #3 $167.62   10.185%   $184.6921   $184.69   $184.70   $184.70  
  Purchase #4 $185.38   8.197%   $200.5756   $200.58   $200.60   $200.60  
  Purchase #5 $230.98   6.684%   $246.4187   $246.42   $246.40   $246.40  
  Purchase #6 $194.26   9.381%   $212.4835   $212.48   $212.50   $212.50  
  Purchase #7 $169.77   6.575%   $180.9324   $180.93   $180.95   $180.90  
  7 purchase totals = $1,361.07       $1,464.2150   $1,464.21   $1,464.25   $1,464.20