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 $184.76   9.794%   $202.8554   $202.86   $202.85   $202.90  
  Purchase #2 $203.25   7.581%   $218.6584   $218.66   $218.65   $218.70  
  Purchase #3 $187.58   8.452%   $203.4343   $203.43   $203.45   $203.40  
  Purchase #4 $167.43   7.370%   $179.7696   $179.77   $179.75   $179.80  
  Purchase #5 $233.34   8.204%   $252.4832   $252.48   $252.50   $252.50  
  Purchase #6 $177.76   13.756%   $202.2127   $202.21   $202.20   $202.20  
  Purchase #7 $188.28   7.337%   $202.0941   $202.09   $202.10   $202.10  
  7 purchase totals = $1,342.40       $1,461.5077   $1,461.50   $1,461.50   $1,461.60