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 $232.69   5.866%   $246.3396   $246.34   $246.35   $246.30  
  Purchase #2 $43.79   13.285%   $49.6075   $49.61   $49.60   $49.60  
  Purchase #3 $50.32   6.335%   $53.5078   $53.51   $53.50   $53.50  
  Purchase #4 $86.63   5.740%   $91.6026   $91.60   $91.60   $91.60  
  Purchase #5 $235.58   3.873%   $244.704   $244.70   $244.70   $244.70  
  Purchase #6 $164.27   11.705%   $183.4978   $183.50   $183.50   $183.50  
  Purchase #7 $211.51   6.861%   $226.0217   $226.02   $226.00   $226.00  
  7 purchase totals = $1,024.79       $1,095.2810   $1,095.28   $1,095.25   $1,095.20