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 $41.69   13.371%   $47.2644   $47.26   $47.25   $47.30  
  Purchase #2 $195.68   11.133%   $217.4651   $217.47   $217.45   $217.50  
  Purchase #3 $167.85   11.813%   $187.6781   $187.68   $187.70   $187.70  
  Purchase #4 $184.36   10.265%   $203.2846   $203.28   $203.30   $203.30  
  Purchase #5 $111.65   11.542%   $124.5366   $124.54   $124.55   $124.50  
  Purchase #6 $122.35   4.243%   $127.5413   $127.54   $127.55   $127.50  
  Purchase #7 $233.45   3.159%   $240.8247   $240.82   $240.80   $240.80  
  7 purchase totals = $1,057.03       $1,148.5948   $1,148.59   $1,148.60   $1,148.60