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 $175.71   11.259%   $195.4932   $195.49   $195.50   $195.50  
  Purchase #2 $185.94   8.802%   $202.3064   $202.31   $202.30   $202.30  
  Purchase #3 $238.61   9.283%   $260.7602   $260.76   $260.75   $260.80  
  Purchase #4 $241.47   9.693%   $264.8757   $264.88   $264.90   $264.90  
  Purchase #5 $179.26   12.275%   $201.2642   $201.26   $201.25   $201.30  
  Purchase #6 $167.61   3.119%   $172.8378   $172.84   $172.85   $172.80  
  Purchase #7 $126.67   7.657%   $136.3691   $136.37   $136.35   $136.40  
  7 purchase totals = $1,315.27       $1,433.9066   $1,433.91   $1,433.90   $1,434.00