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 $85.26   13.167%   $96.4862   $96.49   $96.50   $96.50  
  Purchase #2 $200.35   5.358%   $211.0848   $211.08   $211.10   $211.10  
  Purchase #3 $208.79   3.139%   $215.3439   $215.34   $215.35   $215.30  
  Purchase #4 $178.31   10.195%   $196.4887   $196.49   $196.50   $196.50  
  Purchase #5 $155.50   11.394%   $173.2177   $173.22   $173.20   $173.20  
  Purchase #6 $232.30   3.507%   $240.4468   $240.45   $240.45   $240.40  
  Purchase #7 $124.35   5.115%   $130.7105   $130.71   $130.70   $130.70  
  7 purchase totals = $1,184.86       $1,263.7786   $1,263.78   $1,263.80   $1,263.70