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 $69.76   10.818%   $77.3066   $77.31   $77.30   $77.30  
  Purchase #2 $226.41   10.238%   $249.5899   $249.59   $249.60   $249.60  
  Purchase #3 $142.99   13.151%   $161.7946   $161.79   $161.80   $161.80  
  Purchase #4 $222.61   13.171%   $251.93   $251.93   $251.95   $251.90  
  Purchase #5 $35.86   10.292%   $39.5507   $39.55   $39.55   $39.60  
  Purchase #6 $103.30   11.743%   $115.4305   $115.43   $115.45   $115.40  
  Purchase #7 $213.42   11.855%   $238.7209   $238.72   $238.70   $238.70  
  7 purchase totals = $1,014.35       $1,134.3232   $1,134.32   $1,134.35   $1,134.30