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 $49.26   5.276%   $51.859   $51.86   $51.85   $51.90  
  Purchase #2 $146.34   3.565%   $151.557   $151.56   $151.55   $151.60  
  Purchase #3 $79.53   4.719%   $83.283   $83.28   $83.30   $83.30  
  Purchase #4 $228.78   10.346%   $252.4496   $252.45   $252.45   $252.40  
  Purchase #5 $188.74   9.149%   $206.0078   $206.01   $206.00   $206.00  
  Purchase #6 $103.60   8.157%   $112.0507   $112.05   $112.05   $112.10  
  Purchase #7 $158.33   11.109%   $175.9189   $175.92   $175.90   $175.90  
  7 purchase totals = $954.58       $1,033.1260   $1,033.13   $1,033.10   $1,033.20