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 $243.67   6.806%   $260.2542   $260.25   $260.25   $260.30  
  Purchase #2 $38.81   6.182%   $41.2092   $41.21   $41.20   $41.20  
  Purchase #3 $164.45   10.835%   $182.2682   $182.27   $182.25   $182.30  
  Purchase #4 $198.49   4.731%   $207.8806   $207.88   $207.90   $207.90  
  Purchase #5 $176.62   7.620%   $190.0784   $190.08   $190.10   $190.10  
  Purchase #6 $138.88   10.575%   $153.5666   $153.57   $153.55   $153.60  
  Purchase #7 $178.42   6.815%   $190.5793   $190.58   $190.60   $190.60  
  7 purchase totals = $1,139.34       $1,225.8365   $1,225.84   $1,225.85   $1,226.00