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 $43.34   10.843%   $48.0394   $48.04   $48.05   $48.00  
  Purchase #2 $186.98   10.358%   $206.3474   $206.35   $206.35   $206.30  
  Purchase #3 $60.76   12.645%   $68.4431   $68.44   $68.45   $68.40  
  Purchase #4 $93.71   4.420%   $97.852   $97.85   $97.85   $97.90  
  Purchase #5 $244.73   12.178%   $274.5332   $274.53   $274.55   $274.50  
  Purchase #6 $68.80   6.287%   $73.1255   $73.13   $73.15   $73.10  
  Purchase #7 $5.72   10.716%   $6.333   $6.33   $6.35   $6.30  
  7 purchase totals = $704.04       $774.6736   $774.67   $774.75   $774.50