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 $214.54   8.427%   $232.6193   $232.62   $232.60   $232.60  
  Purchase #2 $34.64   4.679%   $36.2608   $36.26   $36.25   $36.30  
  Purchase #3 $60.73   11.120%   $67.4832   $67.48   $67.50   $67.50  
  Purchase #4 $226.52   12.426%   $254.6674   $254.67   $254.65   $254.70  
  Purchase #5 $199.66   12.563%   $224.7433   $224.74   $224.75   $224.70  
  Purchase #6 $238.41   9.458%   $260.9588   $260.96   $260.95   $261.00  
  Purchase #7 $13.70   5.763%   $14.4895   $14.49   $14.50   $14.50  
  7 purchase totals = $988.20       $1,091.2223   $1,091.22   $1,091.20   $1,091.30