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 $212.39   9.494%   $232.5543   $232.55   $232.55   $232.60  
  Purchase #2 $20.94   11.445%   $23.3366   $23.34   $23.35   $23.30  
  Purchase #3 $220.66   13.303%   $250.0144   $250.01   $250.00   $250.00  
  Purchase #4 $129.91   10.358%   $143.3661   $143.37   $143.35   $143.40  
  Purchase #5 $144.69   4.795%   $151.6279   $151.63   $151.65   $151.60  
  Purchase #6 $173.54   6.703%   $185.1724   $185.17   $185.15   $185.20  
  Purchase #7 $26.62   6.508%   $28.3524   $28.35   $28.35   $28.40  
  7 purchase totals = $928.75       $1,014.4241   $1,014.42   $1,014.40   $1,014.50