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 $62.37   4.144%   $64.9546   $64.95   $64.95   $65.00  
  Purchase #2 $242.87   10.867%   $269.2627   $269.26   $269.25   $269.30  
  Purchase #3 $165.69   12.162%   $185.8412   $185.84   $185.85   $185.80  
  Purchase #4 $164.99   9.653%   $180.9165   $180.92   $180.90   $180.90  
  Purchase #5 $105.70   9.363%   $115.5967   $115.60   $115.60   $115.60  
  Purchase #6 $92.45   13.200%   $104.6534   $104.65   $104.65   $104.70  
  Purchase #7 $177.92   7.593%   $191.4295   $191.43   $191.45   $191.40  
  7 purchase totals = $1,011.99       $1,112.6546   $1,112.65   $1,112.65   $1,112.70