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 $60.94   11.582%   $67.9981   $68.00   $68.00   $68.00  
  Purchase #2 $141.96   4.107%   $147.7903   $147.79   $147.80   $147.80  
  Purchase #3 $70.95   7.737%   $76.4394   $76.44   $76.45   $76.40  
  Purchase #4 $162.66   13.660%   $184.8794   $184.88   $184.90   $184.90  
  Purchase #5 $201.60   3.491%   $208.6379   $208.64   $208.65   $208.60  
  Purchase #6 $82.31   6.147%   $87.3696   $87.37   $87.35   $87.40  
  Purchase #7 $250.89   4.701%   $262.6843   $262.68   $262.70   $262.70  
  7 purchase totals = $971.31       $1,035.7990   $1,035.80   $1,035.85   $1,035.80