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 $107.69   11.115%   $119.6597   $119.66   $119.65   $119.70  
  Purchase #2 $201.99   4.206%   $210.4857   $210.49   $210.50   $210.50  
  Purchase #3 $229.60   7.507%   $246.8361   $246.84   $246.85   $246.80  
  Purchase #4 $219.61   12.244%   $246.499   $246.50   $246.50   $246.50  
  Purchase #5 $54.26   6.219%   $57.6344   $57.63   $57.65   $57.60  
  Purchase #6 $212.36   5.719%   $224.5049   $224.50   $224.50   $224.50  
  Purchase #7 $54.30   12.107%   $60.8741   $60.87   $60.85   $60.90  
  7 purchase totals = $1,079.81       $1,166.4939   $1,166.49   $1,166.50   $1,166.50