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 $178.27   10.266%   $196.5712   $196.57   $196.55   $196.60  
  Purchase #2 $197.69   4.857%   $207.2918   $207.29   $207.30   $207.30  
  Purchase #3 $207.43   5.471%   $218.7785   $218.78   $218.80   $218.80  
  Purchase #4 $47.85   8.832%   $52.0761   $52.08   $52.10   $52.10  
  Purchase #5 $65.44   6.464%   $69.67   $69.67   $69.65   $69.70  
  Purchase #6 $139.37   8.312%   $150.9544   $150.95   $150.95   $151.00  
  Purchase #7 $160.67   10.163%   $176.9989   $177.00   $177.00   $177.00  
  7 purchase totals = $996.72       $1,072.3409   $1,072.34   $1,072.35   $1,072.50