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 $195.50   5.873%   $206.9817   $206.98   $207.00   $207.00  
  Purchase #2 $78.68   10.298%   $86.7825   $86.78   $86.80   $86.80  
  Purchase #3 $124.59   11.102%   $138.422   $138.42   $138.40   $138.40  
  Purchase #4 $63.74   6.335%   $67.7779   $67.78   $67.80   $67.80  
  Purchase #5 $161.81   3.508%   $167.4863   $167.49   $167.50   $167.50  
  Purchase #6 $121.91   3.496%   $126.172   $126.17   $126.15   $126.20  
  Purchase #7 $135.36   11.290%   $150.6421   $150.64   $150.65   $150.60  
  7 purchase totals = $881.59       $944.2645   $944.26   $944.30   $944.30