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 $58.92   5.364%   $62.0805   $62.08   $62.10   $62.10  
  Purchase #2 $43.85   5.481%   $46.2534   $46.25   $46.25   $46.30  
  Purchase #3 $48.41   3.477%   $50.0932   $50.09   $50.10   $50.10  
  Purchase #4 $225.36   13.317%   $255.3712   $255.37   $255.35   $255.40  
  Purchase #5 $62.57   5.681%   $66.1246   $66.12   $66.10   $66.10  
  Purchase #6 $81.53   3.708%   $84.5531   $84.55   $84.55   $84.60  
  Purchase #7 $198.90   12.148%   $223.0624   $223.06   $223.05   $223.10  
  7 purchase totals = $719.54       $787.5384   $787.52   $787.50   $787.70