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 $84.58   12.854%   $95.4519   $95.45   $95.45   $95.50  
  Purchase #2 $8.29   4.857%   $8.6926   $8.69   $8.70   $8.70  
  Purchase #3 $111.80   3.580%   $115.8024   $115.80   $115.80   $115.80  
  Purchase #4 $244.68   9.289%   $267.4083   $267.41   $267.40   $267.40  
  Purchase #5 $216.61   8.495%   $235.011   $235.01   $235.00   $235.00  
  Purchase #6 $40.52   12.636%   $45.6401   $45.64   $45.65   $45.60  
  Purchase #7 $244.66   12.759%   $275.8762   $275.88   $275.90   $275.90  
  7 purchase totals = $951.14       $1,043.8825   $1,043.88   $1,043.90   $1,043.90