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 $196.39   8.249%   $212.5902   $212.59   $212.60   $212.60  
  Purchase #2 $90.69   11.478%   $101.0994   $101.10   $101.10   $101.10  
  Purchase #3 $49.87   7.607%   $53.6636   $53.66   $53.65   $53.70  
  Purchase #4 $107.38   11.442%   $119.6664   $119.67   $119.65   $119.70  
  Purchase #5 $173.98   9.303%   $190.1654   $190.17   $190.15   $190.20  
  Purchase #6 $219.32   3.156%   $226.2417   $226.24   $226.25   $226.20  
  Purchase #7 $233.51   10.536%   $258.1126   $258.11   $258.10   $258.10  
  7 purchase totals = $1,071.14       $1,161.5393   $1,161.54   $1,161.50   $1,161.60