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 $68.43   12.332%   $76.8688   $76.87   $76.85   $76.90  
  Purchase #2 $203.96   4.423%   $212.9812   $212.98   $213.00   $213.00  
  Purchase #3 $247.53   9.373%   $270.731   $270.73   $270.75   $270.70  
  Purchase #4 $90.86   13.408%   $103.0425   $103.04   $103.05   $103.00  
  Purchase #5 $125.83   9.453%   $137.7247   $137.72   $137.70   $137.70  
  Purchase #6 $217.60   13.754%   $247.5287   $247.53   $247.55   $247.50  
  Purchase #7 $60.74   10.847%   $67.3285   $67.33   $67.35   $67.30  
  7 purchase totals = $1,014.95       $1,116.2054   $1,116.20   $1,116.25   $1,116.10