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 $85.38   13.256%   $96.698   $96.70   $96.70   $96.70  
  Purchase #2 $170.99   3.807%   $177.4996   $177.50   $177.50   $177.50  
  Purchase #3 $175.82   10.334%   $193.9892   $193.99   $194.00   $194.00  
  Purchase #4 $136.56   9.608%   $149.6807   $149.68   $149.70   $149.70  
  Purchase #5 $161.27   11.683%   $180.1112   $180.11   $180.10   $180.10  
  Purchase #6 $89.82   4.158%   $93.5547   $93.55   $93.55   $93.60  
  Purchase #7 $166.88   5.862%   $176.6625   $176.66   $176.65   $176.70  
  7 purchase totals = $986.72       $1,068.1959   $1,068.19   $1,068.20   $1,068.30