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 $88.94   5.260%   $93.6182   $93.62   $93.60   $93.60  
  Purchase #2 $226.45   4.328%   $236.2508   $236.25   $236.25   $236.30  
  Purchase #3 $168.33   8.168%   $182.0792   $182.08   $182.10   $182.10  
  Purchase #4 $99.31   6.866%   $106.1286   $106.13   $106.15   $106.10  
  Purchase #5 $244.69   6.587%   $260.8077   $260.81   $260.80   $260.80  
  Purchase #6 $183.70   7.140%   $196.8162   $196.82   $196.80   $196.80  
  Purchase #7 $66.60   13.611%   $75.6649   $75.66   $75.65   $75.70  
  7 purchase totals = $1,078.02       $1,151.3656   $1,151.37   $1,151.35   $1,151.40