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 $68.35   7.165%   $73.2473   $73.25   $73.25   $73.20  
  Purchase #2 $135.31   11.425%   $150.7692   $150.77   $150.75   $150.80  
  Purchase #3 $189.62   6.522%   $201.987   $201.99   $202.00   $202.00  
  Purchase #4 $223.28   11.807%   $249.6427   $249.64   $249.65   $249.60  
  Purchase #5 $219.64   6.210%   $233.2796   $233.28   $233.30   $233.30  
  Purchase #6 $55.79   5.734%   $58.989   $58.99   $59.00   $59.00  
  Purchase #7 $44.57   5.757%   $47.1359   $47.14   $47.15   $47.10  
  7 purchase totals = $936.56       $1,015.0507   $1,015.06   $1,015.10   $1,015.00