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 $167.97   3.694%   $174.1748   $174.17   $174.15   $174.20  
  Purchase #2 $206.46   4.525%   $215.8023   $215.80   $215.80   $215.80  
  Purchase #3 $179.91   9.474%   $196.9547   $196.95   $196.95   $197.00  
  Purchase #4 $30.97   7.106%   $33.1707   $33.17   $33.15   $33.20  
  Purchase #5 $106.69   9.256%   $116.5652   $116.57   $116.55   $116.60  
  Purchase #6 $220.34   11.472%   $245.6174   $245.62   $245.60   $245.60  
  Purchase #7 $38.39   9.141%   $41.8992   $41.90   $41.90   $41.90  
  7 purchase totals = $950.73       $1,024.1843   $1,024.18   $1,024.10   $1,024.30