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 $44.97   7.509%   $48.3468   $48.35   $48.35   $48.30  
  Purchase #2 $211.47   7.749%   $227.8568   $227.86   $227.85   $227.90  
  Purchase #3 $192.41   10.668%   $212.9363   $212.94   $212.95   $212.90  
  Purchase #4 $177.66   6.244%   $188.7531   $188.75   $188.75   $188.80  
  Purchase #5 $63.77   11.646%   $71.1967   $71.20   $71.20   $71.20  
  Purchase #6 $39.27   11.687%   $43.8595   $43.86   $43.85   $43.90  
  Purchase #7 $229.95   9.535%   $251.8757   $251.88   $251.90   $251.90  
  7 purchase totals = $959.50       $1,044.8249   $1,044.84   $1,044.85   $1,044.90