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 $214.66   7.405%   $230.5556   $230.56   $230.55   $230.60  
  Purchase #2 $245.34   9.624%   $268.9515   $268.95   $268.95   $269.00  
  Purchase #3 $210.98   7.432%   $226.66   $226.66   $226.65   $226.70  
  Purchase #4 $34.44   3.362%   $35.5979   $35.60   $35.60   $35.60  
  Purchase #5 $220.79   3.139%   $227.7206   $227.72   $227.70   $227.70  
  Purchase #6 $48.37   12.835%   $54.5783   $54.58   $54.60   $54.60  
  Purchase #7 $192.35   13.480%   $218.2788   $218.28   $218.30   $218.30  
  7 purchase totals = $1,166.93       $1,262.3427   $1,262.35   $1,262.35   $1,262.50