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 $193.33   7.409%   $207.6538   $207.65   $207.65   $207.70  
  Purchase #2 $76.96   3.334%   $79.5258   $79.53   $79.55   $79.50  
  Purchase #3 $214.60   9.781%   $235.59   $235.59   $235.60   $235.60  
  Purchase #4 $83.90   13.183%   $94.9605   $94.96   $94.95   $95.00  
  Purchase #5 $120.90   8.211%   $130.8271   $130.83   $130.85   $130.80  
  Purchase #6 $70.85   6.245%   $75.2746   $75.27   $75.25   $75.30  
  Purchase #7 $65.80   3.501%   $68.1037   $68.10   $68.10   $68.10  
  7 purchase totals = $826.34       $891.9355   $891.93   $891.95   $892.00