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 $69.64   9.113%   $75.9863   $75.99   $76.00   $76.00  
  Purchase #2 $206.57   8.766%   $224.6779   $224.68   $224.70   $224.70  
  Purchase #3 $141.83   9.775%   $155.6939   $155.69   $155.70   $155.70  
  Purchase #4 $25.35   4.267%   $26.4317   $26.43   $26.45   $26.40  
  Purchase #5 $235.64   3.318%   $243.4585   $243.46   $243.45   $243.50  
  Purchase #6 $93.42   6.351%   $99.3531   $99.35   $99.35   $99.40  
  Purchase #7 $99.81   6.734%   $106.5312   $106.53   $106.55   $106.50  
  7 purchase totals = $872.26       $932.1326   $932.13   $932.20   $932.20