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 $39.67   12.680%   $44.7002   $44.70   $44.70   $44.70  
  Purchase #2 $130.85   3.382%   $135.2753   $135.28   $135.30   $135.30  
  Purchase #3 $169.40   5.414%   $178.5713   $178.57   $178.55   $178.60  
  Purchase #4 $250.42   9.230%   $273.5338   $273.53   $273.55   $273.50  
  Purchase #5 $115.97   4.843%   $121.5864   $121.59   $121.60   $121.60  
  Purchase #6 $238.66   10.502%   $263.7241   $263.72   $263.70   $263.70  
  Purchase #7 $186.77   3.591%   $193.4769   $193.48   $193.50   $193.50  
  7 purchase totals = $1,131.74       $1,210.8680   $1,210.87   $1,210.90   $1,210.90