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 $60.81   5.434%   $64.1144   $64.11   $64.10   $64.10  
  Purchase #2 $212.83   12.670%   $239.7956   $239.80   $239.80   $239.80  
  Purchase #3 $120.42   9.359%   $131.6901   $131.69   $131.70   $131.70  
  Purchase #4 $51.99   8.491%   $56.4045   $56.40   $56.40   $56.40  
  Purchase #5 $212.84   6.384%   $226.4277   $226.43   $226.45   $226.40  
  Purchase #6 $218.60   10.516%   $241.588   $241.59   $241.60   $241.60  
  Purchase #7 $211.87   4.639%   $221.6986   $221.70   $221.70   $221.70  
  7 purchase totals = $1,089.36       $1,181.7189   $1,181.72   $1,181.75   $1,181.70