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 $68.82   10.553%   $76.0826   $76.08   $76.10   $76.10  
  Purchase #2 $14.84   4.783%   $15.5498   $15.55   $15.55   $15.50  
  Purchase #3 $22.37   10.610%   $24.7435   $24.74   $24.75   $24.70  
  Purchase #4 $155.80   7.378%   $167.2949   $167.29   $167.30   $167.30  
  Purchase #5 $40.27   5.640%   $42.5412   $42.54   $42.55   $42.50  
  Purchase #6 $103.61   12.168%   $116.2173   $116.22   $116.20   $116.20  
  Purchase #7 $209.54   12.391%   $235.5041   $235.50   $235.50   $235.50  
  7 purchase totals = $615.25       $677.9334   $677.92   $677.95   $677.80