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 $96.29   7.866%   $103.8642   $103.86   $103.85   $103.90  
  Purchase #2 $185.43   11.557%   $206.8601   $206.86   $206.85   $206.90  
  Purchase #3 $85.45   11.134%   $94.964   $94.96   $94.95   $95.00  
  Purchase #4 $79.36   8.367%   $86.0001   $86.00   $86.00   $86.00  
  Purchase #5 $176.40   5.135%   $185.4581   $185.46   $185.45   $185.50  
  Purchase #6 $190.71   6.226%   $202.5836   $202.58   $202.60   $202.60  
  Purchase #7 $225.98   4.303%   $235.7039   $235.70   $235.70   $235.70  
  7 purchase totals = $1,039.62       $1,115.4340   $1,115.42   $1,115.40   $1,115.60