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 $71.58   5.694%   $75.6558   $75.66   $75.65   $75.70  
  Purchase #2 $110.26   12.249%   $123.7657   $123.77   $123.75   $123.80  
  Purchase #3 $177.89   12.242%   $199.6673   $199.67   $199.65   $199.70  
  Purchase #4 $113.71   7.356%   $122.0745   $122.07   $122.05   $122.10  
  Purchase #5 $100.69   13.771%   $114.556   $114.56   $114.55   $114.60  
  Purchase #6 $205.57   4.687%   $215.2051   $215.21   $215.20   $215.20  
  Purchase #7 $172.28   7.259%   $184.7858   $184.79   $184.80   $184.80  
  7 purchase totals = $951.98       $1,035.7102   $1,035.73   $1,035.65   $1,035.90