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 $238.80   9.685%   $261.9278   $261.93   $261.95   $261.90  
  Purchase #2 $25.35   4.437%   $26.4748   $26.47   $26.45   $26.50  
  Purchase #3 $90.70   5.809%   $95.9688   $95.97   $95.95   $96.00  
  Purchase #4 $236.43   11.163%   $262.8227   $262.82   $262.80   $262.80  
  Purchase #5 $181.45   5.464%   $191.3644   $191.36   $191.35   $191.40  
  Purchase #6 $80.96   6.241%   $86.0127   $86.01   $86.00   $86.00  
  Purchase #7 $184.98   11.359%   $205.9919   $205.99   $206.00   $206.00  
  7 purchase totals = $1,038.67       $1,130.5631   $1,130.55   $1,130.50   $1,130.60