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 $192.57   4.415%   $201.072   $201.07   $201.05   $201.10  
  Purchase #2 $106.37   11.168%   $118.2494   $118.25   $118.25   $118.20  
  Purchase #3 $66.63   10.626%   $73.7101   $73.71   $73.70   $73.70  
  Purchase #4 $142.80   12.750%   $161.007   $161.01   $161.00   $161.00  
  Purchase #5 $99.91   9.827%   $109.7282   $109.73   $109.75   $109.70  
  Purchase #6 $239.91   13.869%   $273.1831   $273.18   $273.20   $273.20  
  Purchase #7 $198.83   5.384%   $209.535   $209.54   $209.55   $209.50  
  7 purchase totals = $1,047.02       $1,146.4848   $1,146.49   $1,146.50   $1,146.40