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 $211.47   8.576%   $229.6057   $229.61   $229.60   $229.60  
  Purchase #2 $113.31   5.423%   $119.4548   $119.45   $119.45   $119.50  
  Purchase #3 $20.69   7.800%   $22.3038   $22.30   $22.30   $22.30  
  Purchase #4 $204.47   4.429%   $213.526   $213.53   $213.55   $213.50  
  Purchase #5 $202.84   13.266%   $229.7488   $229.75   $229.75   $229.70  
  Purchase #6 $105.43   8.315%   $114.1965   $114.20   $114.20   $114.20  
  Purchase #7 $95.86   7.694%   $103.2355   $103.24   $103.25   $103.20  
  7 purchase totals = $954.07       $1,032.0711   $1,032.08   $1,032.10   $1,032.00