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 $236.86   4.617%   $247.7958   $247.80   $247.80   $247.80  
  Purchase #2 $23.57   7.175%   $25.2611   $25.26   $25.25   $25.30  
  Purchase #3 $182.70   5.491%   $192.7321   $192.73   $192.75   $192.70  
  Purchase #4 $139.46   7.538%   $149.9725   $149.97   $149.95   $150.00  
  Purchase #5 $230.68   7.504%   $247.9902   $247.99   $248.00   $248.00  
  Purchase #6 $135.92   6.546%   $144.8173   $144.82   $144.80   $144.80  
  Purchase #7 $116.61   3.533%   $120.7298   $120.73   $120.75   $120.70  
  7 purchase totals = $1,065.80       $1,129.2988   $1,129.30   $1,129.30   $1,129.30