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 $62.95   5.694%   $66.5344   $66.53   $66.55   $66.50  
  Purchase #2 $81.83   5.517%   $86.3446   $86.34   $86.35   $86.30  
  Purchase #3 $193.97   9.648%   $212.6842   $212.68   $212.70   $212.70  
  Purchase #4 $220.26   3.791%   $228.6101   $228.61   $228.60   $228.60  
  Purchase #5 $11.80   9.235%   $12.8897   $12.89   $12.90   $12.90  
  Purchase #6 $246.75   12.144%   $276.7153   $276.72   $276.70   $276.70  
  Purchase #7 $144.69   4.559%   $151.2864   $151.29   $151.30   $151.30  
  7 purchase totals = $962.25       $1,035.0647   $1,035.06   $1,035.10   $1,035.00