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 $191.63   6.244%   $203.5954   $203.60   $203.60   $203.60  
  Purchase #2 $120.51   9.488%   $131.944   $131.94   $131.95   $131.90  
  Purchase #3 $60.88   11.184%   $67.6888   $67.69   $67.70   $67.70  
  Purchase #4 $163.86   3.114%   $168.9626   $168.96   $168.95   $169.00  
  Purchase #5 $131.47   10.777%   $145.6385   $145.64   $145.65   $145.60  
  Purchase #6 $150.73   4.466%   $157.4616   $157.46   $157.45   $157.50  
  Purchase #7 $224.78   4.647%   $235.2255   $235.23   $235.25   $235.20  
  7 purchase totals = $1,043.86       $1,110.5164   $1,110.52   $1,110.55   $1,110.50