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 $91.34   4.481%   $95.4329   $95.43   $95.45   $95.40  
  Purchase #2 $198.86   9.294%   $217.342   $217.34   $217.35   $217.30  
  Purchase #3 $185.63   4.184%   $193.3968   $193.40   $193.40   $193.40  
  Purchase #4 $48.79   4.229%   $50.8533   $50.85   $50.85   $50.90  
  Purchase #5 $137.31   10.371%   $151.5504   $151.55   $151.55   $151.60  
  Purchase #6 $230.67   12.424%   $259.3284   $259.33   $259.35   $259.30  
  Purchase #7 $94.74   6.750%   $101.135   $101.14   $101.15   $101.10  
  7 purchase totals = $987.34       $1,069.0388   $1,069.04   $1,069.10   $1,069.00