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 $202.56   11.210%   $225.267   $225.27   $225.25   $225.30  
  Purchase #2 $184.29   8.323%   $199.6285   $199.63   $199.65   $199.60  
  Purchase #3 $158.45   8.457%   $171.8501   $171.85   $171.85   $171.90  
  Purchase #4 $130.43   6.530%   $138.9471   $138.95   $138.95   $138.90  
  Purchase #5 $72.65   3.723%   $75.3548   $75.35   $75.35   $75.40  
  Purchase #6 $75.34   12.123%   $84.4735   $84.47   $84.45   $84.50  
  Purchase #7 $198.58   8.315%   $215.0919   $215.09   $215.10   $215.10  
  7 purchase totals = $1,022.30       $1,110.6129   $1,110.61   $1,110.60   $1,110.70