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 $158.31   6.563%   $168.6999   $168.70   $168.70   $168.70  
  Purchase #2 $143.32   12.532%   $161.2809   $161.28   $161.30   $161.30  
  Purchase #3 $70.46   3.656%   $73.036   $73.04   $73.05   $73.00  
  Purchase #4 $38.39   9.356%   $41.9818   $41.98   $42.00   $42.00  
  Purchase #5 $221.42   13.651%   $251.646   $251.65   $251.65   $251.60  
  Purchase #6 $237.99   6.508%   $253.4784   $253.48   $253.50   $253.50  
  Purchase #7 $208.49   7.522%   $224.1726   $224.17   $224.15   $224.20  
  7 purchase totals = $1,078.38       $1,174.2956   $1,174.30   $1,174.35   $1,174.30