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 $235.37   4.670%   $246.3618   $246.36   $246.35   $246.40  
  Purchase #2 $24.89   4.402%   $25.9857   $25.99   $26.00   $26.00  
  Purchase #3 $56.44   4.834%   $59.1683   $59.17   $59.15   $59.20  
  Purchase #4 $244.47   5.512%   $257.9452   $257.95   $257.95   $257.90  
  Purchase #5 $198.97   3.811%   $206.5527   $206.55   $206.55   $206.60  
  Purchase #6 $125.57   12.189%   $140.8757   $140.88   $140.90   $140.90  
  Purchase #7 $101.55   6.716%   $108.3701   $108.37   $108.35   $108.40  
  7 purchase totals = $987.26       $1,045.2595   $1,045.27   $1,045.25   $1,045.40