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 $197.54   5.311%   $208.0313   $208.03   $208.05   $208.00  
  Purchase #2 $183.75   7.670%   $197.8436   $197.84   $197.85   $197.80  
  Purchase #3 $46.30   10.819%   $51.3092   $51.31   $51.30   $51.30  
  Purchase #4 $48.99   12.712%   $55.2176   $55.22   $55.20   $55.20  
  Purchase #5 $239.59   8.364%   $259.6293   $259.63   $259.65   $259.60  
  Purchase #6 $213.52   11.605%   $238.299   $238.30   $238.30   $238.30  
  Purchase #7 $12.75   12.147%   $14.2987   $14.30   $14.30   $14.30  
  7 purchase totals = $942.44       $1,024.6287   $1,024.63   $1,024.65   $1,024.50