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 $182.64   7.123%   $195.6494   $195.65   $195.65   $195.60  
  Purchase #2 $235.99   4.338%   $246.2272   $246.23   $246.25   $246.20  
  Purchase #3 $37.99   5.678%   $40.1471   $40.15   $40.15   $40.10  
  Purchase #4 $240.44   13.462%   $272.808   $272.81   $272.80   $272.80  
  Purchase #5 $69.48   8.617%   $75.4671   $75.47   $75.45   $75.50  
  Purchase #6 $56.33   12.722%   $63.4963   $63.50   $63.50   $63.50  
  Purchase #7 $118.36   8.857%   $128.8431   $128.84   $128.85   $128.80  
  7 purchase totals = $941.23       $1,022.6382   $1,022.65   $1,022.65   $1,022.50