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 $214.77   13.638%   $244.0603   $244.06   $244.05   $244.10  
  Purchase #2 $192.99   4.804%   $202.2612   $202.26   $202.25   $202.30  
  Purchase #3 $47.80   8.748%   $51.9815   $51.98   $52.00   $52.00  
  Purchase #4 $61.73   12.106%   $69.203   $69.20   $69.20   $69.20  
  Purchase #5 $213.30   13.313%   $241.6966   $241.70   $241.70   $241.70  
  Purchase #6 $166.30   13.392%   $188.5709   $188.57   $188.55   $188.60  
  Purchase #7 $132.85   4.108%   $138.3075   $138.31   $138.30   $138.30  
  7 purchase totals = $1,029.74       $1,136.0810   $1,136.08   $1,136.05   $1,136.20