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 $194.61   9.120%   $212.3584   $212.36   $212.35   $212.40  
  Purchase #2 $67.54   9.230%   $73.7739   $73.77   $73.75   $73.80  
  Purchase #3 $111.49   4.423%   $116.4212   $116.42   $116.40   $116.40  
  Purchase #4 $207.26   5.380%   $218.4106   $218.41   $218.40   $218.40  
  Purchase #5 $62.29   13.251%   $70.544   $70.54   $70.55   $70.50  
  Purchase #6 $179.93   10.184%   $198.2541   $198.25   $198.25   $198.30  
  Purchase #7 $128.79   11.209%   $143.2261   $143.23   $143.25   $143.20  
  7 purchase totals = $951.91       $1,032.9883   $1,032.98   $1,032.95   $1,033.00