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 $208.59   5.840%   $220.7717   $220.77   $220.75   $220.80  
  Purchase #2 $237.67   7.133%   $254.623   $254.62   $254.60   $254.60  
  Purchase #3 $153.69   5.125%   $161.5666   $161.57   $161.55   $161.60  
  Purchase #4 $38.44   7.103%   $41.1704   $41.17   $41.15   $41.20  
  Purchase #5 $215.56   3.512%   $223.1305   $223.13   $223.15   $223.10  
  Purchase #6 $233.66   6.570%   $249.0115   $249.01   $249.00   $249.00  
  Purchase #7 $10.96   13.355%   $12.4237   $12.42   $12.40   $12.40  
  7 purchase totals = $1,098.57       $1,162.6974   $1,162.69   $1,162.60   $1,162.70