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 $88.92   9.603%   $97.459   $97.46   $97.45   $97.50  
  Purchase #2 $123.51   3.315%   $127.6044   $127.60   $127.60   $127.60  
  Purchase #3 $47.80   6.832%   $51.0657   $51.07   $51.05   $51.10  
  Purchase #4 $240.63   4.454%   $251.3477   $251.35   $251.35   $251.30  
  Purchase #5 $196.78   8.851%   $214.197   $214.20   $214.20   $214.20  
  Purchase #6 $48.99   8.331%   $53.0714   $53.07   $53.05   $53.10  
  Purchase #7 $89.63   12.603%   $100.9261   $100.93   $100.95   $100.90  
  7 purchase totals = $836.26       $895.6713   $895.68   $895.65   $895.70