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 $89.66   7.309%   $96.2132   $96.21   $96.20   $96.20  
  Purchase #2 $234.40   4.806%   $245.6653   $245.67   $245.65   $245.70  
  Purchase #3 $214.67   8.177%   $232.2236   $232.22   $232.20   $232.20  
  Purchase #4 $110.37   11.520%   $123.0846   $123.08   $123.10   $123.10  
  Purchase #5 $46.40   5.606%   $49.0012   $49.00   $49.00   $49.00  
  Purchase #6 $234.62   7.271%   $251.6792   $251.68   $251.70   $251.70  
  Purchase #7 $189.55   7.733%   $204.2079   $204.21   $204.20   $204.20  
  7 purchase totals = $1,119.67       $1,202.0750   $1,202.07   $1,202.05   $1,202.10