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 $213.92   10.628%   $236.6554   $236.66   $236.65   $236.70  
  Purchase #2 $103.87   3.425%   $107.4275   $107.43   $107.45   $107.40  
  Purchase #3 $84.95   6.486%   $90.4599   $90.46   $90.45   $90.50  
  Purchase #4 $158.81   11.601%   $177.2335   $177.23   $177.25   $177.20  
  Purchase #5 $194.60   7.728%   $209.6387   $209.64   $209.65   $209.60  
  Purchase #6 $110.94   6.402%   $118.0424   $118.04   $118.05   $118.00  
  Purchase #7 $109.93   9.331%   $120.1876   $120.19   $120.20   $120.20  
  7 purchase totals = $977.02       $1,059.6450   $1,059.65   $1,059.70   $1,059.60