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 $87.97   8.527%   $95.4712   $95.47   $95.45   $95.50  
  Purchase #2 $76.84   6.858%   $82.1097   $82.11   $82.10   $82.10  
  Purchase #3 $17.36   13.204%   $19.6522   $19.65   $19.65   $19.70  
  Purchase #4 $203.77   3.594%   $211.0935   $211.09   $211.10   $211.10  
  Purchase #5 $156.49   5.235%   $164.6823   $164.68   $164.70   $164.70  
  Purchase #6 $215.71   6.687%   $230.1345   $230.13   $230.15   $230.10  
  Purchase #7 $185.68   13.589%   $210.9121   $210.91   $210.90   $210.90  
  7 purchase totals = $943.82       $1,014.0555   $1,014.04   $1,014.05   $1,014.10