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 $5.41   9.567%   $5.9276   $5.93   $5.95   $5.90  
  Purchase #2 $95.40   8.636%   $103.6387   $103.64   $103.65   $103.60  
  Purchase #3 $102.31   8.488%   $110.9941   $110.99   $111.00   $111.00  
  Purchase #4 $190.90   7.716%   $205.6298   $205.63   $205.65   $205.60  
  Purchase #5 $109.43   13.586%   $124.2972   $124.30   $124.30   $124.30  
  Purchase #6 $238.35   6.606%   $254.0954   $254.10   $254.10   $254.10  
  Purchase #7 $201.78   3.832%   $209.5122   $209.51   $209.50   $209.50  
  7 purchase totals = $943.58       $1,014.0950   $1,014.10   $1,014.15   $1,014.00