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 $216.99   13.191%   $245.6132   $245.61   $245.60   $245.60  
  Purchase #2 $95.73   9.765%   $105.078   $105.08   $105.10   $105.10  
  Purchase #3 $178.96   10.796%   $198.2805   $198.28   $198.30   $198.30  
  Purchase #4 $241.75   3.576%   $250.395   $250.40   $250.40   $250.40  
  Purchase #5 $112.32   12.370%   $126.214   $126.21   $126.20   $126.20  
  Purchase #6 $234.49   4.277%   $244.5191   $244.52   $244.50   $244.50  
  Purchase #7 $72.71   5.497%   $76.7069   $76.71   $76.70   $76.70  
  7 purchase totals = $1,152.95       $1,246.8067   $1,246.81   $1,246.80   $1,246.80