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 $60.51   3.575%   $62.6732   $62.67   $62.65   $62.70  
  Purchase #2 $85.90   11.298%   $95.605   $95.61   $95.60   $95.60  
  Purchase #3 $94.32   7.364%   $101.2657   $101.27   $101.25   $101.30  
  Purchase #4 $131.68   10.837%   $145.9502   $145.95   $145.95   $146.00  
  Purchase #5 $208.25   4.357%   $217.3235   $217.32   $217.30   $217.30  
  Purchase #6 $198.85   9.498%   $217.7368   $217.74   $217.75   $217.70  
  Purchase #7 $216.28   12.121%   $242.4953   $242.50   $242.50   $242.50  
  7 purchase totals = $995.79       $1,083.0497   $1,083.06   $1,083.00   $1,083.10