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 $144.77   3.124%   $149.2926   $149.29   $149.30   $149.30  
  Purchase #2 $186.81   4.423%   $195.0726   $195.07   $195.05   $195.10  
  Purchase #3 $70.72   4.441%   $73.8607   $73.86   $73.85   $73.90  
  Purchase #4 $200.39   6.182%   $212.7781   $212.78   $212.80   $212.80  
  Purchase #5 $209.78   10.419%   $231.637   $231.64   $231.65   $231.60  
  Purchase #6 $161.69   4.520%   $168.9984   $169.00   $169.00   $169.00  
  Purchase #7 $80.46   3.291%   $83.1079   $83.11   $83.10   $83.10  
  7 purchase totals = $1,054.62       $1,114.7473   $1,114.75   $1,114.75   $1,114.80