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 $114.36   7.611%   $123.0639   $123.06   $123.05   $123.10  
  Purchase #2 $233.46   5.560%   $246.4404   $246.44   $246.45   $246.40  
  Purchase #3 $57.39   11.107%   $63.7643   $63.76   $63.75   $63.80  
  Purchase #4 $214.27   5.463%   $225.9756   $225.98   $226.00   $226.00  
  Purchase #5 $57.34   12.105%   $64.281   $64.28   $64.30   $64.30  
  Purchase #6 $177.36   9.196%   $193.67   $193.67   $193.65   $193.70  
  Purchase #7 $223.81   8.747%   $243.3867   $243.39   $243.40   $243.40  
  7 purchase totals = $1,077.99       $1,160.5819   $1,160.58   $1,160.60   $1,160.70