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 $196.93   4.556%   $205.9021   $205.90   $205.90   $205.90  
  Purchase #2 $219.72   3.258%   $226.8785   $226.88   $226.90   $226.90  
  Purchase #3 $117.80   10.597%   $130.2833   $130.28   $130.30   $130.30  
  Purchase #4 $112.48   8.280%   $121.7933   $121.79   $121.80   $121.80  
  Purchase #5 $32.87   11.358%   $36.6034   $36.60   $36.60   $36.60  
  Purchase #6 $111.79   11.586%   $124.742   $124.74   $124.75   $124.70  
  Purchase #7 $232.90   8.290%   $252.2074   $252.21   $252.20   $252.20  
  7 purchase totals = $1,024.49       $1,098.4100   $1,098.40   $1,098.45   $1,098.40