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 $163.82   10.340%   $180.759   $180.76   $180.75   $180.80  
  Purchase #2 $85.59   6.722%   $91.3434   $91.34   $91.35   $91.30  
  Purchase #3 $80.49   4.300%   $83.9511   $83.95   $83.95   $84.00  
  Purchase #4 $215.52   5.356%   $227.0633   $227.06   $227.05   $227.10  
  Purchase #5 $156.99   11.744%   $175.4269   $175.43   $175.45   $175.40  
  Purchase #6 $190.25   12.759%   $214.524   $214.52   $214.50   $214.50  
  Purchase #7 $75.83   6.196%   $80.5284   $80.53   $80.55   $80.50  
  7 purchase totals = $968.49       $1,053.5961   $1,053.59   $1,053.60   $1,053.60