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 $41.50   11.608%   $46.3173   $46.32   $46.30   $46.30  
  Purchase #2 $220.73   4.280%   $230.1772   $230.18   $230.20   $230.20  
  Purchase #3 $14.55   6.746%   $15.5315   $15.53   $15.55   $15.50  
  Purchase #4 $209.77   8.106%   $226.774   $226.77   $226.75   $226.80  
  Purchase #5 $39.65   8.698%   $43.0988   $43.10   $43.10   $43.10  
  Purchase #6 $177.86   10.335%   $196.2418   $196.24   $196.25   $196.20  
  Purchase #7 $227.90   4.693%   $238.5953   $238.60   $238.60   $238.60  
  7 purchase totals = $931.96       $996.7359   $996.74   $996.75   $996.70