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 $178.45   9.697%   $195.7543   $195.75   $195.75   $195.80  
  Purchase #2 $56.81   12.493%   $63.9073   $63.91   $63.90   $63.90  
  Purchase #3 $233.45   5.357%   $245.9559   $245.96   $245.95   $246.00  
  Purchase #4 $137.39   5.749%   $145.2886   $145.29   $145.30   $145.30  
  Purchase #5 $12.70   7.662%   $13.6731   $13.67   $13.65   $13.70  
  Purchase #6 $209.80   11.838%   $234.6361   $234.64   $234.65   $234.60  
  Purchase #7 $123.52   8.601%   $134.144   $134.14   $134.15   $134.10  
  7 purchase totals = $952.12       $1,033.3593   $1,033.36   $1,033.35   $1,033.40