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 $92.97   3.234%   $95.9766   $95.98   $96.00   $96.00  
  Purchase #2 $5.48   10.337%   $6.0465   $6.05   $6.05   $6.00  
  Purchase #3 $214.37   9.662%   $235.0824   $235.08   $235.10   $235.10  
  Purchase #4 $61.58   12.196%   $69.0903   $69.09   $69.10   $69.10  
  Purchase #5 $221.25   9.737%   $242.7931   $242.79   $242.80   $242.80  
  Purchase #6 $138.56   12.417%   $155.765   $155.77   $155.75   $155.80  
  Purchase #7 $113.70   12.813%   $128.2684   $128.27   $128.25   $128.30  
  7 purchase totals = $847.91       $933.0223   $933.03   $933.05   $933.10