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 $90.36   4.307%   $94.2518   $94.25   $94.25   $94.30  
  Purchase #2 $24.86   3.272%   $25.6734   $25.67   $25.65   $25.70  
  Purchase #3 $210.90   11.178%   $234.4744   $234.47   $234.45   $234.50  
  Purchase #4 $42.74   11.521%   $47.6641   $47.66   $47.65   $47.70  
  Purchase #5 $183.74   12.240%   $206.2298   $206.23   $206.25   $206.20  
  Purchase #6 $220.88   4.595%   $231.0294   $231.03   $231.05   $231.00  
  Purchase #7 $188.35   10.226%   $207.6107   $207.61   $207.60   $207.60  
  7 purchase totals = $961.83       $1,046.9336   $1,046.92   $1,046.90   $1,047.00