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 $61.95   12.742%   $69.8437   $69.84   $69.85   $69.80  
  Purchase #2 $195.25   6.414%   $207.7733   $207.77   $207.75   $207.80  
  Purchase #3 $164.41   11.344%   $183.0607   $183.06   $183.05   $183.10  
  Purchase #4 $191.70   8.177%   $207.3753   $207.38   $207.40   $207.40  
  Purchase #5 $72.51   12.601%   $81.647   $81.65   $81.65   $81.60  
  Purchase #6 $194.41   10.267%   $214.3701   $214.37   $214.35   $214.40  
  Purchase #7 $235.69   4.251%   $245.7092   $245.71   $245.70   $245.70  
  7 purchase totals = $1,115.92       $1,209.7793   $1,209.78   $1,209.75   $1,209.80