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 $58.76   7.371%   $63.0912   $63.09   $63.10   $63.10  
  Purchase #2 $158.80   5.581%   $167.6626   $167.66   $167.65   $167.70  
  Purchase #3 $188.42   6.631%   $200.9141   $200.91   $200.90   $200.90  
  Purchase #4 $44.94   4.637%   $47.0239   $47.02   $47.00   $47.00  
  Purchase #5 $68.25   9.135%   $74.4846   $74.48   $74.50   $74.50  
  Purchase #6 $225.48   11.739%   $251.9491   $251.95   $251.95   $251.90  
  Purchase #7 $206.69   9.767%   $226.8774   $226.88   $226.90   $226.90  
  7 purchase totals = $951.34       $1,032.0029   $1,031.99   $1,032.00   $1,032.00