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 $69.82   8.142%   $75.5047   $75.50   $75.50   $75.50  
  Purchase #2 $177.36   7.704%   $191.0238   $191.02   $191.00   $191.00  
  Purchase #3 $78.58   5.209%   $82.6732   $82.67   $82.65   $82.70  
  Purchase #4 $88.56   5.616%   $93.5335   $93.53   $93.55   $93.50  
  Purchase #5 $79.47   9.834%   $87.2851   $87.29   $87.30   $87.30  
  Purchase #6 $111.96   11.632%   $124.9832   $124.98   $125.00   $125.00  
  Purchase #7 $90.57   7.197%   $97.0883   $97.09   $97.10   $97.10  
  7 purchase totals = $696.32       $752.0918   $752.08   $752.10   $752.10