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 $222.26   10.584%   $245.784   $245.78   $245.80   $245.80  
  Purchase #2 $43.40   12.194%   $48.6922   $48.69   $48.70   $48.70  
  Purchase #3 $81.49   13.804%   $92.7389   $92.74   $92.75   $92.70  
  Purchase #4 $11.81   11.125%   $13.1239   $13.12   $13.10   $13.10  
  Purchase #5 $187.35   10.768%   $207.5238   $207.52   $207.50   $207.50  
  Purchase #6 $222.58   5.336%   $234.4569   $234.46   $234.45   $234.50  
  Purchase #7 $183.51   4.633%   $192.012   $192.01   $192.00   $192.00  
  7 purchase totals = $952.40       $1,034.3317   $1,034.32   $1,034.30   $1,034.30