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 $86.66   10.551%   $95.8035   $95.80   $95.80   $95.80  
  Purchase #2 $177.60   13.347%   $201.3043   $201.30   $201.30   $201.30  
  Purchase #3 $61.65   6.530%   $65.6757   $65.68   $65.70   $65.70  
  Purchase #4 $106.43   5.484%   $112.2666   $112.27   $112.25   $112.30  
  Purchase #5 $230.82   12.842%   $260.4619   $260.46   $260.45   $260.50  
  Purchase #6 $223.67   5.151%   $235.1912   $235.19   $235.20   $235.20  
  Purchase #7 $137.69   7.652%   $148.226   $148.23   $148.25   $148.20  
  7 purchase totals = $1,024.52       $1,118.9292   $1,118.93   $1,118.95   $1,119.00