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 $77.85   13.718%   $88.5295   $88.53   $88.55   $88.50  
  Purchase #2 $117.83   5.603%   $124.432   $124.43   $124.45   $124.40  
  Purchase #3 $201.71   3.289%   $208.3442   $208.34   $208.35   $208.30  
  Purchase #4 $161.63   7.206%   $173.2771   $173.28   $173.30   $173.30  
  Purchase #5 $89.56   6.848%   $95.6931   $95.69   $95.70   $95.70  
  Purchase #6 $186.96   12.725%   $210.7507   $210.75   $210.75   $210.80  
  Purchase #7 $140.56   13.261%   $159.1997   $159.20   $159.20   $159.20  
  7 purchase totals = $976.10       $1,060.2263   $1,060.22   $1,060.30   $1,060.20