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 $213.75   9.593%   $234.255   $234.26   $234.25   $234.30  
  Purchase #2 $166.27   9.157%   $181.4953   $181.50   $181.50   $181.50  
  Purchase #3 $144.34   9.675%   $158.3049   $158.30   $158.30   $158.30  
  Purchase #4 $89.92   5.321%   $94.7046   $94.70   $94.70   $94.70  
  Purchase #5 $129.66   5.691%   $137.039   $137.04   $137.05   $137.00  
  Purchase #6 $232.51   9.365%   $254.2846   $254.28   $254.30   $254.30  
  Purchase #7 $90.82   12.662%   $102.3196   $102.32   $102.30   $102.30  
  7 purchase totals = $1,067.27       $1,162.4030   $1,162.40   $1,162.40   $1,162.40