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 $53.48   10.418%   $59.0515   $59.05   $59.05   $59.10  
  Purchase #2 $217.65   6.871%   $232.6047   $232.60   $232.60   $232.60  
  Purchase #3 $62.47   8.172%   $67.575   $67.58   $67.60   $67.60  
  Purchase #4 $233.76   12.808%   $263.7   $263.70   $263.70   $263.70  
  Purchase #5 $143.58   8.501%   $155.7857   $155.79   $155.80   $155.80  
  Purchase #6 $17.25   11.694%   $19.2672   $19.27   $19.25   $19.30  
  Purchase #7 $228.29   10.580%   $252.4431   $252.44   $252.45   $252.40  
  7 purchase totals = $956.48       $1,050.4272   $1,050.43   $1,050.45   $1,050.50