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 $196.84   4.662%   $206.0167   $206.02   $206.00   $206.00  
  Purchase #2 $235.33   13.281%   $266.5842   $266.58   $266.60   $266.60  
  Purchase #3 $210.63   7.122%   $225.6311   $225.63   $225.65   $225.60  
  Purchase #4 $144.67   3.113%   $149.1736   $149.17   $149.15   $149.20  
  Purchase #5 $134.31   6.710%   $143.3222   $143.32   $143.30   $143.30  
  Purchase #6 $188.48   4.675%   $197.2914   $197.29   $197.30   $197.30  
  Purchase #7 $16.49   6.233%   $17.5178   $17.52   $17.50   $17.50  
  7 purchase totals = $1,126.75       $1,205.5370   $1,205.53   $1,205.50   $1,205.50