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 $38.77   7.711%   $41.7596   $41.76   $41.75   $41.80  
  Purchase #2 $55.42   11.314%   $61.6902   $61.69   $61.70   $61.70  
  Purchase #3 $114.27   10.844%   $126.6614   $126.66   $126.65   $126.70  
  Purchase #4 $131.98   6.474%   $140.5244   $140.52   $140.50   $140.50  
  Purchase #5 $93.98   10.108%   $103.4795   $103.48   $103.50   $103.50  
  Purchase #6 $195.82   4.325%   $204.2892   $204.29   $204.30   $204.30  
  Purchase #7 $68.25   7.624%   $73.4534   $73.45   $73.45   $73.50  
  7 purchase totals = $698.49       $751.8577   $751.85   $751.85   $752.00