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 $167.56   11.414%   $186.6853   $186.69   $186.70   $186.70  
  Purchase #2 $172.48   10.525%   $190.6335   $190.63   $190.65   $190.60  
  Purchase #3 $169.84   5.150%   $178.5868   $178.59   $178.60   $178.60  
  Purchase #4 $106.39   8.359%   $115.2831   $115.28   $115.30   $115.30  
  Purchase #5 $63.32   13.544%   $71.8961   $71.90   $71.90   $71.90  
  Purchase #6 $109.84   9.525%   $120.3023   $120.30   $120.30   $120.30  
  Purchase #7 $235.74   11.441%   $262.711   $262.71   $262.70   $262.70  
  7 purchase totals = $1,025.17       $1,126.0981   $1,126.10   $1,126.15   $1,126.10