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 $76.42   13.787%   $86.956   $86.96   $86.95   $87.00  
  Purchase #2 $182.67   12.237%   $205.0233   $205.02   $205.00   $205.00  
  Purchase #3 $241.84   11.204%   $268.9358   $268.94   $268.95   $268.90  
  Purchase #4 $193.86   8.105%   $209.5724   $209.57   $209.55   $209.60  
  Purchase #5 $153.72   11.872%   $171.9696   $171.97   $171.95   $172.00  
  Purchase #6 $231.45   8.513%   $251.1533   $251.15   $251.15   $251.20  
  Purchase #7 $212.63   3.582%   $220.2464   $220.25   $220.25   $220.20  
  7 purchase totals = $1,292.59       $1,413.8568   $1,413.86   $1,413.80   $1,413.90