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 $194.36   3.658%   $201.4697   $201.47   $201.45   $201.50  
  Purchase #2 $77.46   13.283%   $87.749   $87.75   $87.75   $87.70  
  Purchase #3 $57.46   10.590%   $63.545   $63.55   $63.55   $63.50  
  Purchase #4 $34.34   3.104%   $35.4059   $35.41   $35.40   $35.40  
  Purchase #5 $244.30   3.571%   $253.024   $253.02   $253.00   $253.00  
  Purchase #6 $43.45   6.767%   $46.3903   $46.39   $46.40   $46.40  
  Purchase #7 $84.91   11.685%   $94.8317   $94.83   $94.85   $94.80  
  7 purchase totals = $736.28       $782.4156   $782.42   $782.40   $782.30