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 $85.81   11.865%   $95.9914   $95.99   $96.00   $96.00  
  Purchase #2 $69.93   6.128%   $74.2153   $74.22   $74.20   $74.20  
  Purchase #3 $213.34   9.352%   $233.2916   $233.29   $233.30   $233.30  
  Purchase #4 $118.50   11.134%   $131.6938   $131.69   $131.70   $131.70  
  Purchase #5 $120.82   3.330%   $124.8433   $124.84   $124.85   $124.80  
  Purchase #6 $217.65   13.326%   $246.654   $246.65   $246.65   $246.70  
  Purchase #7 $111.49   12.237%   $125.133   $125.13   $125.15   $125.10  
  7 purchase totals = $937.54       $1,031.8224   $1,031.81   $1,031.85   $1,031.80