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 $62.27   11.604%   $69.4958   $69.50   $69.50   $69.50  
  Purchase #2 $113.73   3.232%   $117.4058   $117.41   $117.40   $117.40  
  Purchase #3 $168.70   4.320%   $175.9878   $175.99   $176.00   $176.00  
  Purchase #4 $84.95   6.732%   $90.6688   $90.67   $90.65   $90.70  
  Purchase #5 $100.27   7.196%   $107.4854   $107.49   $107.50   $107.50  
  Purchase #6 $190.64   7.547%   $205.0276   $205.03   $205.05   $205.00  
  Purchase #7 $63.47   9.310%   $69.3791   $69.38   $69.40   $69.40  
  7 purchase totals = $784.03       $835.4503   $835.47   $835.50   $835.50