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 $176.34   11.858%   $197.2504   $197.25   $197.25   $197.30  
  Purchase #2 $209.49   10.703%   $231.9117   $231.91   $231.90   $231.90  
  Purchase #3 $174.84   4.386%   $182.5085   $182.51   $182.50   $182.50  
  Purchase #4 $241.54   11.303%   $268.8413   $268.84   $268.85   $268.80  
  Purchase #5 $239.78   12.176%   $268.9756   $268.98   $269.00   $269.00  
  Purchase #6 $248.66   4.288%   $259.3225   $259.32   $259.30   $259.30  
  Purchase #7 $199.47   6.672%   $212.7786   $212.78   $212.80   $212.80  
  7 purchase totals = $1,490.12       $1,621.5886   $1,621.59   $1,621.60   $1,621.60