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 $167.30   6.153%   $177.594   $177.59   $177.60   $177.60  
  Purchase #2 $94.55   13.670%   $107.475   $107.48   $107.50   $107.50  
  Purchase #3 $49.35   4.663%   $51.6512   $51.65   $51.65   $51.70  
  Purchase #4 $248.40   8.660%   $269.9114   $269.91   $269.90   $269.90  
  Purchase #5 $150.93   6.412%   $160.6076   $160.61   $160.60   $160.60  
  Purchase #6 $245.69   12.217%   $275.7059   $275.71   $275.70   $275.70  
  Purchase #7 $5.41   10.110%   $5.957   $5.96   $5.95   $6.00  
  7 purchase totals = $961.63       $1,048.9021   $1,048.91   $1,048.90   $1,049.00