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 $53.98   13.704%   $61.3774   $61.38   $61.40   $61.40  
  Purchase #2 $233.56   5.467%   $246.3287   $246.33   $246.35   $246.30  
  Purchase #3 $33.95   6.260%   $36.0753   $36.08   $36.10   $36.10  
  Purchase #4 $33.34   6.289%   $35.4368   $35.44   $35.45   $35.40  
  Purchase #5 $152.61   13.526%   $173.252   $173.25   $173.25   $173.30  
  Purchase #6 $247.32   5.809%   $261.6868   $261.69   $261.70   $261.70  
  Purchase #7 $203.71   9.857%   $223.7897   $223.79   $223.80   $223.80  
  7 purchase totals = $958.47       $1,037.9467   $1,037.96   $1,038.05   $1,038.00