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 $84.44   12.418%   $94.9258   $94.93   $94.95   $94.90  
  Purchase #2 $80.93   8.562%   $87.8592   $87.86   $87.85   $87.90  
  Purchase #3 $208.89   7.757%   $225.0936   $225.09   $225.10   $225.10  
  Purchase #4 $82.83   7.712%   $89.2178   $89.22   $89.20   $89.20  
  Purchase #5 $168.94   4.521%   $176.5778   $176.58   $176.60   $176.60  
  Purchase #6 $31.76   3.793%   $32.9647   $32.96   $32.95   $33.00  
  Purchase #7 $168.30   10.369%   $185.751   $185.75   $185.75   $185.80  
  7 purchase totals = $826.09       $892.3899   $892.39   $892.40   $892.50