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 $85.93   11.420%   $95.7432   $95.74   $95.75   $95.70  
  Purchase #2 $10.28   4.564%   $10.7492   $10.75   $10.75   $10.70  
  Purchase #3 $49.67   6.182%   $52.7406   $52.74   $52.75   $52.70  
  Purchase #4 $212.94   13.216%   $241.0822   $241.08   $241.10   $241.10  
  Purchase #5 $76.44   10.301%   $84.3141   $84.31   $84.30   $84.30  
  Purchase #6 $9.70   4.110%   $10.0987   $10.10   $10.10   $10.10  
  Purchase #7 $192.35   4.137%   $200.3075   $200.31   $200.30   $200.30  
  7 purchase totals = $637.31       $695.0355   $695.03   $695.05   $694.90