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 $32.58   4.495%   $34.0445   $34.04   $34.05   $34.00  
  Purchase #2 $244.65   12.635%   $275.5615   $275.56   $275.55   $275.60  
  Purchase #3 $142.39   10.703%   $157.63   $157.63   $157.65   $157.60  
  Purchase #4 $245.66   4.131%   $255.8082   $255.81   $255.80   $255.80  
  Purchase #5 $236.74   3.634%   $245.3431   $245.34   $245.35   $245.30  
  Purchase #6 $11.70   10.554%   $12.9348   $12.93   $12.95   $12.90  
  Purchase #7 $33.87   5.719%   $35.807   $35.81   $35.80   $35.80  
  7 purchase totals = $947.59       $1,017.1291   $1,017.12   $1,017.15   $1,017.00