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 $84.69   12.773%   $95.5075   $95.51   $95.50   $95.50  
  Purchase #2 $184.31   13.296%   $208.8159   $208.82   $208.80   $208.80  
  Purchase #3 $194.29   7.132%   $208.1468   $208.15   $208.15   $208.10  
  Purchase #4 $67.30   11.838%   $75.267   $75.27   $75.25   $75.30  
  Purchase #5 $189.81   3.223%   $195.9276   $195.93   $195.95   $195.90  
  Purchase #6 $213.43   9.659%   $234.0452   $234.05   $234.05   $234.00  
  Purchase #7 $77.81   12.771%   $87.7471   $87.75   $87.75   $87.70  
  7 purchase totals = $1,011.64       $1,105.4571   $1,105.48   $1,105.45   $1,105.30