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 $23.37   11.716%   $26.108   $26.11   $26.10   $26.10  
  Purchase #2 $204.40   5.335%   $215.3047   $215.30   $215.30   $215.30  
  Purchase #3 $86.87   5.448%   $91.6027   $91.60   $91.60   $91.60  
  Purchase #4 $149.58   11.457%   $166.7174   $166.72   $166.70   $166.70  
  Purchase #5 $205.67   7.854%   $221.8233   $221.82   $221.80   $221.80  
  Purchase #6 $132.96   9.806%   $145.9981   $146.00   $146.00   $146.00  
  Purchase #7 $182.94   12.609%   $206.0069   $206.01   $206.00   $206.00  
  7 purchase totals = $985.79       $1,073.5611   $1,073.56   $1,073.50   $1,073.50