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 $190.48   5.669%   $201.2783   $201.28   $201.30   $201.30  
  Purchase #2 $192.50   8.393%   $208.6565   $208.66   $208.65   $208.70  
  Purchase #3 $32.30   11.452%   $35.999   $36.00   $36.00   $36.00  
  Purchase #4 $61.38   5.572%   $64.8001   $64.80   $64.80   $64.80  
  Purchase #5 $137.89   8.573%   $149.7113   $149.71   $149.70   $149.70  
  Purchase #6 $193.74   11.564%   $216.1441   $216.14   $216.15   $216.10  
  Purchase #7 $120.27   6.135%   $127.6486   $127.65   $127.65   $127.60  
  7 purchase totals = $928.56       $1,004.2379   $1,004.24   $1,004.25   $1,004.20