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 $69.37   9.831%   $76.1898   $76.19   $76.20   $76.20  
  Purchase #2 $117.98   13.256%   $133.6194   $133.62   $133.60   $133.60  
  Purchase #3 $149.59   9.312%   $163.5198   $163.52   $163.50   $163.50  
  Purchase #4 $178.77   10.607%   $197.7321   $197.73   $197.75   $197.70  
  Purchase #5 $127.36   9.488%   $139.4439   $139.44   $139.45   $139.40  
  Purchase #6 $208.49   6.125%   $221.26   $221.26   $221.25   $221.30  
  Purchase #7 $25.91   13.303%   $29.3568   $29.36   $29.35   $29.40  
  7 purchase totals = $877.47       $961.1218   $961.12   $961.10   $961.10