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 $216.64   9.697%   $237.6476   $237.65   $237.65   $237.60  
  Purchase #2 $124.94   4.706%   $130.8197   $130.82   $130.80   $130.80  
  Purchase #3 $193.39   9.861%   $212.4602   $212.46   $212.45   $212.50  
  Purchase #4 $222.57   4.587%   $232.7793   $232.78   $232.80   $232.80  
  Purchase #5 $105.65   10.497%   $116.7401   $116.74   $116.75   $116.70  
  Purchase #6 $150.61   11.481%   $167.9015   $167.90   $167.90   $167.90  
  Purchase #7 $53.28   7.614%   $57.3367   $57.34   $57.35   $57.30  
  7 purchase totals = $1,067.08       $1,155.6851   $1,155.69   $1,155.70   $1,155.60