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 $82.41   5.510%   $86.9508   $86.95   $86.95   $87.00  
  Purchase #2 $184.63   11.377%   $205.6354   $205.64   $205.65   $205.60  
  Purchase #3 $179.49   11.463%   $200.0649   $200.06   $200.05   $200.10  
  Purchase #4 $240.26   7.163%   $257.4698   $257.47   $257.45   $257.50  
  Purchase #5 $81.66   12.611%   $91.9581   $91.96   $91.95   $92.00  
  Purchase #6 $237.88   5.166%   $250.1689   $250.17   $250.15   $250.20  
  Purchase #7 $99.70   9.447%   $109.1187   $109.12   $109.10   $109.10  
  7 purchase totals = $1,106.03       $1,201.3666   $1,201.37   $1,201.30   $1,201.50