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 $105.57   4.424%   $110.2404   $110.24   $110.25   $110.20  
  Purchase #2 $186.48   5.106%   $196.0017   $196.00   $196.00   $196.00  
  Purchase #3 $77.98   6.329%   $82.9154   $82.92   $82.90   $82.90  
  Purchase #4 $151.81   5.614%   $160.3326   $160.33   $160.35   $160.30  
  Purchase #5 $119.45   6.113%   $126.752   $126.75   $126.75   $126.80  
  Purchase #6 $60.91   8.548%   $66.1166   $66.12   $66.10   $66.10  
  Purchase #7 $197.37   5.649%   $208.5194   $208.52   $208.50   $208.50  
  7 purchase totals = $899.57       $950.8781   $950.88   $950.85   $950.80