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 $56.44   11.135%   $62.7246   $62.72   $62.70   $62.70  
  Purchase #2 $219.66   7.198%   $235.4711   $235.47   $235.45   $235.50  
  Purchase #3 $64.68   7.512%   $69.5388   $69.54   $69.55   $69.50  
  Purchase #4 $86.56   13.472%   $98.2214   $98.22   $98.20   $98.20  
  Purchase #5 $192.69   12.352%   $216.4911   $216.49   $216.50   $216.50  
  Purchase #6 $197.43   8.526%   $214.2629   $214.26   $214.25   $214.30  
  Purchase #7 $135.45   12.712%   $152.6684   $152.67   $152.65   $152.70  
  7 purchase totals = $952.91       $1,049.3783   $1,049.37   $1,049.30   $1,049.40