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 $194.61   5.834%   $205.9635   $205.96   $205.95   $206.00  
  Purchase #2 $115.88   3.117%   $119.492   $119.49   $119.50   $119.50  
  Purchase #3 $207.32   5.575%   $218.8781   $218.88   $218.90   $218.90  
  Purchase #4 $209.72   8.265%   $227.0534   $227.05   $227.05   $227.10  
  Purchase #5 $235.90   10.564%   $260.8205   $260.82   $260.80   $260.80  
  Purchase #6 $124.68   8.243%   $134.9574   $134.96   $134.95   $135.00  
  Purchase #7 $120.74   6.300%   $128.3466   $128.35   $128.35   $128.30  
  7 purchase totals = $1,208.85       $1,295.5115   $1,295.51   $1,295.50   $1,295.60