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 $82.35   3.265%   $85.0387   $85.04   $85.05   $85.00  
  Purchase #2 $117.41   7.284%   $125.9621   $125.96   $125.95   $126.00  
  Purchase #3 $71.91   3.216%   $74.2226   $74.22   $74.20   $74.20  
  Purchase #4 $188.71   8.167%   $204.1219   $204.12   $204.10   $204.10  
  Purchase #5 $213.35   7.123%   $228.5469   $228.55   $228.55   $228.50  
  Purchase #6 $207.34   13.688%   $235.7207   $235.72   $235.70   $235.70  
  Purchase #7 $165.70   4.772%   $173.6072   $173.61   $173.60   $173.60  
  7 purchase totals = $1,046.77       $1,127.2201   $1,127.22   $1,127.15   $1,127.10