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 $97.85   8.846%   $106.5058   $106.51   $106.50   $106.50  
  Purchase #2 $187.66   4.266%   $195.6656   $195.67   $195.65   $195.70  
  Purchase #3 $46.72   8.785%   $50.8244   $50.82   $50.80   $50.80  
  Purchase #4 $231.56   8.794%   $251.9234   $251.92   $251.90   $251.90  
  Purchase #5 $244.74   9.285%   $267.4641   $267.46   $267.45   $267.50  
  Purchase #6 $152.75   11.782%   $170.747   $170.75   $170.75   $170.70  
  Purchase #7 $216.57   4.636%   $226.6102   $226.61   $226.60   $226.60  
  7 purchase totals = $1,177.85       $1,269.7405   $1,269.74   $1,269.65   $1,269.70