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 $87.51   8.765%   $95.1803   $95.18   $95.20   $95.20  
  Purchase #2 $167.78   4.651%   $175.5834   $175.58   $175.60   $175.60  
  Purchase #3 $182.70   8.807%   $198.7904   $198.79   $198.80   $198.80  
  Purchase #4 $219.38   3.312%   $226.6459   $226.65   $226.65   $226.60  
  Purchase #5 $145.27   9.313%   $158.799   $158.80   $158.80   $158.80  
  Purchase #6 $55.91   3.759%   $58.0117   $58.01   $58.00   $58.00  
  Purchase #7 $72.82   13.579%   $82.7082   $82.71   $82.70   $82.70  
  7 purchase totals = $931.37       $995.7189   $995.72   $995.75   $995.70