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 $32.39   11.868%   $36.234   $36.23   $36.25   $36.20  
  Purchase #2 $148.56   13.637%   $168.8191   $168.82   $168.80   $168.80  
  Purchase #3 $166.55   12.758%   $187.7984   $187.80   $187.80   $187.80  
  Purchase #4 $226.36   13.823%   $257.6497   $257.65   $257.65   $257.60  
  Purchase #5 $199.94   11.765%   $223.4629   $223.46   $223.45   $223.50  
  Purchase #6 $231.38   6.647%   $246.7598   $246.76   $246.75   $246.80  
  Purchase #7 $232.60   3.869%   $241.5993   $241.60   $241.60   $241.60  
  7 purchase totals = $1,237.78       $1,362.3232   $1,362.32   $1,362.30   $1,362.30