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 $244.83   10.137%   $269.6484   $269.65   $269.65   $269.60  
  Purchase #2 $115.35   5.859%   $122.1084   $122.11   $122.10   $122.10  
  Purchase #3 $123.78   5.870%   $131.0459   $131.05   $131.05   $131.00  
  Purchase #4 $45.83   5.492%   $48.347   $48.35   $48.35   $48.30  
  Purchase #5 $227.92   8.301%   $246.8396   $246.84   $246.85   $246.80  
  Purchase #6 $173.41   4.530%   $181.2655   $181.27   $181.25   $181.30  
  Purchase #7 $45.66   4.260%   $47.6051   $47.61   $47.60   $47.60  
  7 purchase totals = $976.78       $1,046.8599   $1,046.88   $1,046.85   $1,046.70