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 $70.31   4.710%   $73.6216   $73.62   $73.60   $73.60  
  Purchase #2 $149.63   9.364%   $163.6414   $163.64   $163.65   $163.60  
  Purchase #3 $175.83   9.345%   $192.2613   $192.26   $192.25   $192.30  
  Purchase #4 $22.33   4.353%   $23.302   $23.30   $23.30   $23.30  
  Purchase #5 $160.33   6.716%   $171.0978   $171.10   $171.10   $171.10  
  Purchase #6 $242.57   8.253%   $262.5893   $262.59   $262.60   $262.60  
  Purchase #7 $137.93   9.148%   $150.5478   $150.55   $150.55   $150.50  
  7 purchase totals = $958.93       $1,037.0612   $1,037.06   $1,037.05   $1,037.00