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 $65.60   10.683%   $72.608   $72.61   $72.60   $72.60  
  Purchase #2 $178.66   9.344%   $195.354   $195.35   $195.35   $195.40  
  Purchase #3 $54.62   9.833%   $59.9908   $59.99   $60.00   $60.00  
  Purchase #4 $24.43   10.708%   $27.046   $27.05   $27.05   $27.00  
  Purchase #5 $84.48   10.758%   $93.5684   $93.57   $93.55   $93.60  
  Purchase #6 $120.27   9.783%   $132.036   $132.04   $132.05   $132.00  
  Purchase #7 $212.83   12.862%   $240.2042   $240.20   $240.20   $240.20  
  7 purchase totals = $740.89       $820.8074   $820.81   $820.80   $820.80