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 $201.63   7.492%   $216.7361   $216.74   $216.75   $216.70  
  Purchase #2 $7.56   6.549%   $8.0551   $8.06   $8.05   $8.10  
  Purchase #3 $65.31   9.144%   $71.2819   $71.28   $71.30   $71.30  
  Purchase #4 $62.62   6.333%   $66.5857   $66.59   $66.60   $66.60  
  Purchase #5 $82.78   4.539%   $86.5374   $86.54   $86.55   $86.50  
  Purchase #6 $55.80   13.807%   $63.5043   $63.50   $63.50   $63.50  
  Purchase #7 $233.74   5.478%   $246.5443   $246.54   $246.55   $246.50  
  7 purchase totals = $709.44       $759.2448   $759.25   $759.30   $759.20