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 $88.41   8.833%   $96.2193   $96.22   $96.20   $96.20  
  Purchase #2 $226.43   4.573%   $236.7846   $236.78   $236.80   $236.80  
  Purchase #3 $113.88   9.447%   $124.6382   $124.64   $124.65   $124.60  
  Purchase #4 $190.25   7.246%   $204.0355   $204.04   $204.05   $204.00  
  Purchase #5 $177.37   10.298%   $195.6356   $195.64   $195.65   $195.60  
  Purchase #6 $119.94   7.821%   $129.3205   $129.32   $129.30   $129.30  
  Purchase #7 $160.94   10.161%   $177.2931   $177.29   $177.30   $177.30  
  7 purchase totals = $1,077.22       $1,163.9268   $1,163.93   $1,163.95   $1,163.80