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 $23.84   9.321%   $26.0621   $26.06   $26.05   $26.10  
  Purchase #2 $98.51   13.290%   $111.602   $111.60   $111.60   $111.60  
  Purchase #3 $244.31   9.168%   $266.7083   $266.71   $266.70   $266.70  
  Purchase #4 $8.57   5.254%   $9.0203   $9.02   $9.00   $9.00  
  Purchase #5 $159.32   5.306%   $167.7735   $167.77   $167.75   $167.80  
  Purchase #6 $200.34   8.108%   $216.5836   $216.58   $216.60   $216.60  
  Purchase #7 $210.66   7.642%   $226.7586   $226.76   $226.75   $226.80  
  7 purchase totals = $945.55       $1,024.5084   $1,024.50   $1,024.45   $1,024.60