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 $76.28   12.553%   $85.8554   $85.86   $85.85   $85.90  
  Purchase #2 $141.98   9.329%   $155.2253   $155.23   $155.25   $155.20  
  Purchase #3 $23.89   9.733%   $26.2152   $26.22   $26.20   $26.20  
  Purchase #4 $148.59   3.153%   $153.275   $153.28   $153.30   $153.30  
  Purchase #5 $80.87   9.204%   $88.3133   $88.31   $88.30   $88.30  
  Purchase #6 $200.69   12.258%   $225.2906   $225.29   $225.30   $225.30  
  Purchase #7 $172.67   11.234%   $192.0677   $192.07   $192.05   $192.10  
  7 purchase totals = $844.97       $926.2425   $926.26   $926.25   $926.30