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 $196.60   7.808%   $211.9505   $211.95   $211.95   $212.00  
  Purchase #2 $74.61   10.788%   $82.6589   $82.66   $82.65   $82.70  
  Purchase #3 $209.41   6.577%   $223.1829   $223.18   $223.20   $223.20  
  Purchase #4 $67.26   3.872%   $69.8643   $69.86   $69.85   $69.90  
  Purchase #5 $212.28   13.204%   $240.3095   $240.31   $240.30   $240.30  
  Purchase #6 $23.52   7.569%   $25.3002   $25.30   $25.30   $25.30  
  Purchase #7 $223.91   10.863%   $248.2333   $248.23   $248.25   $248.20  
  7 purchase totals = $1,007.59       $1,101.4996   $1,101.49   $1,101.50   $1,101.60