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 $90.36   13.576%   $102.6273   $102.63   $102.65   $102.60  
  Purchase #2 $223.59   13.825%   $254.5013   $254.50   $254.50   $254.50  
  Purchase #3 $116.99   6.722%   $124.8541   $124.85   $124.85   $124.90  
  Purchase #4 $241.58   4.344%   $252.0742   $252.07   $252.05   $252.10  
  Purchase #5 $68.80   6.455%   $73.241   $73.24   $73.25   $73.20  
  Purchase #6 $80.87   5.216%   $85.0882   $85.09   $85.10   $85.10  
  Purchase #7 $197.55   3.224%   $203.919   $203.92   $203.90   $203.90  
  7 purchase totals = $1,019.74       $1,096.3051   $1,096.30   $1,096.30   $1,096.30