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 $192.45   4.196%   $200.5252   $200.53   $200.55   $200.50  
  Purchase #2 $227.50   8.463%   $246.7533   $246.75   $246.75   $246.80  
  Purchase #3 $87.50   10.393%   $96.5939   $96.59   $96.60   $96.60  
  Purchase #4 $169.45   12.307%   $190.3042   $190.30   $190.30   $190.30  
  Purchase #5 $65.45   4.793%   $68.587   $68.59   $68.60   $68.60  
  Purchase #6 $129.25   13.719%   $146.9818   $146.98   $147.00   $147.00  
  Purchase #7 $239.67   5.357%   $252.5091   $252.51   $252.50   $252.50  
  7 purchase totals = $1,111.27       $1,202.2545   $1,202.25   $1,202.30   $1,202.30