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 $43.83   10.232%   $48.3147   $48.31   $48.30   $48.30  
  Purchase #2 $172.94   11.277%   $192.4424   $192.44   $192.45   $192.40  
  Purchase #3 $220.45   5.802%   $233.2405   $233.24   $233.25   $233.20  
  Purchase #4 $208.47   11.606%   $232.665   $232.67   $232.65   $232.70  
  Purchase #5 $172.90   6.835%   $184.7177   $184.72   $184.70   $184.70  
  Purchase #6 $132.99   5.676%   $140.5385   $140.54   $140.55   $140.50  
  Purchase #7 $83.79   9.660%   $91.8841   $91.88   $91.90   $91.90  
  7 purchase totals = $1,035.37       $1,123.8029   $1,123.80   $1,123.80   $1,123.70