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 $54.76   7.796%   $59.0291   $59.03   $59.05   $59.00  
  Purchase #2 $194.79   11.843%   $217.859   $217.86   $217.85   $217.90  
  Purchase #3 $249.69   10.235%   $275.2458   $275.25   $275.25   $275.20  
  Purchase #4 $244.82   10.258%   $269.9336   $269.93   $269.95   $269.90  
  Purchase #5 $90.33   5.197%   $95.0245   $95.02   $95.00   $95.00  
  Purchase #6 $238.39   5.159%   $250.6885   $250.69   $250.70   $250.70  
  Purchase #7 $167.68   11.113%   $186.3143   $186.31   $186.30   $186.30  
  7 purchase totals = $1,240.46       $1,354.0948   $1,354.09   $1,354.10   $1,354.00