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 $66.50   11.572%   $74.1954   $74.20   $74.20   $74.20  
  Purchase #2 $116.74   5.655%   $123.3416   $123.34   $123.35   $123.30  
  Purchase #3 $178.25   3.798%   $185.0199   $185.02   $185.00   $185.00  
  Purchase #4 $134.81   12.596%   $151.7907   $151.79   $151.80   $151.80  
  Purchase #5 $172.58   5.758%   $182.5172   $182.52   $182.50   $182.50  
  Purchase #6 $239.85   5.848%   $253.8764   $253.88   $253.90   $253.90  
  Purchase #7 $112.99   10.277%   $124.602   $124.60   $124.60   $124.60  
  7 purchase totals = $1,021.72       $1,095.3432   $1,095.35   $1,095.35   $1,095.30