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 $32.41   8.547%   $35.1801   $35.18   $35.20   $35.20  
  Purchase #2 $97.58   13.304%   $110.562   $110.56   $110.55   $110.60  
  Purchase #3 $151.32   11.286%   $168.398   $168.40   $168.40   $168.40  
  Purchase #4 $17.56   8.628%   $19.0751   $19.08   $19.10   $19.10  
  Purchase #5 $235.64   10.156%   $259.5716   $259.57   $259.55   $259.60  
  Purchase #6 $203.34   4.507%   $212.5045   $212.50   $212.50   $212.50  
  Purchase #7 $86.80   3.758%   $90.0619   $90.06   $90.05   $90.10  
  7 purchase totals = $824.65       $895.3532   $895.35   $895.35   $895.50