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 $47.68   11.605%   $53.2133   $53.21   $53.20   $53.20  
  Purchase #2 $168.26   5.609%   $177.6977   $177.70   $177.70   $177.70  
  Purchase #3 $48.94   6.275%   $52.011   $52.01   $52.00   $52.00  
  Purchase #4 $245.43   7.325%   $263.4077   $263.41   $263.40   $263.40  
  Purchase #5 $237.92   11.843%   $266.0969   $266.10   $266.10   $266.10  
  Purchase #6 $79.45   3.661%   $82.3587   $82.36   $82.35   $82.40  
  Purchase #7 $246.43   11.144%   $273.8922   $273.89   $273.90   $273.90  
  7 purchase totals = $1,074.11       $1,168.6775   $1,168.68   $1,168.65   $1,168.70