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 $61.52   11.529%   $68.6126   $68.61   $68.60   $68.60  
  Purchase #2 $199.68   13.445%   $226.527   $226.53   $226.55   $226.50  
  Purchase #3 $202.72   9.765%   $222.5156   $222.52   $222.50   $222.50  
  Purchase #4 $228.35   5.411%   $240.706   $240.71   $240.70   $240.70  
  Purchase #5 $249.71   13.756%   $284.0601   $284.06   $284.05   $284.10  
  Purchase #6 $202.37   10.832%   $224.2907   $224.29   $224.30   $224.30  
  Purchase #7 $152.56   6.336%   $162.2262   $162.23   $162.25   $162.20  
  7 purchase totals = $1,296.91       $1,428.9382   $1,428.95   $1,428.95   $1,428.90