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 $216.58   8.349%   $234.6623   $234.66   $234.65   $234.70  
  Purchase #2 $246.75   8.337%   $267.3215   $267.32   $267.30   $267.30  
  Purchase #3 $152.52   5.872%   $161.476   $161.48   $161.50   $161.50  
  Purchase #4 $198.77   4.255%   $207.2277   $207.23   $207.25   $207.20  
  Purchase #5 $75.81   12.343%   $85.1672   $85.17   $85.15   $85.20  
  Purchase #6 $101.90   9.385%   $111.4633   $111.46   $111.45   $111.50  
  Purchase #7 $125.45   6.776%   $133.9505   $133.95   $133.95   $134.00  
  7 purchase totals = $1,117.78       $1,201.2685   $1,201.27   $1,201.25   $1,201.40