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 $33.85   5.672%   $35.77   $35.77   $35.75   $35.80  
  Purchase #2 $246.41   5.152%   $259.105   $259.11   $259.10   $259.10  
  Purchase #3 $152.77   3.112%   $157.5242   $157.52   $157.50   $157.50  
  Purchase #4 $245.95   6.699%   $262.4262   $262.43   $262.45   $262.40  
  Purchase #5 $202.82   5.397%   $213.7662   $213.77   $213.75   $213.80  
  Purchase #6 $243.87   6.447%   $259.5923   $259.59   $259.60   $259.60  
  Purchase #7 $45.88   11.501%   $51.1567   $51.16   $51.15   $51.20  
  7 purchase totals = $1,171.55       $1,239.3406   $1,239.35   $1,239.30   $1,239.40