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 $195.61   9.669%   $214.5235   $214.52   $214.50   $214.50  
  Purchase #2 $229.87   6.575%   $244.984   $244.98   $245.00   $245.00  
  Purchase #3 $53.38   6.377%   $56.784   $56.78   $56.80   $56.80  
  Purchase #4 $110.85   5.820%   $117.3015   $117.30   $117.30   $117.30  
  Purchase #5 $118.29   5.483%   $124.7758   $124.78   $124.80   $124.80  
  Purchase #6 $134.76   6.189%   $143.1003   $143.10   $143.10   $143.10  
  Purchase #7 $48.55   6.697%   $51.8014   $51.80   $51.80   $51.80  
  7 purchase totals = $891.31       $953.2705   $953.26   $953.30   $953.30