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 $212.45   11.661%   $237.2238   $237.22   $237.20   $237.20  
  Purchase #2 $115.80   12.523%   $130.3016   $130.30   $130.30   $130.30  
  Purchase #3 $207.57   10.536%   $229.4396   $229.44   $229.45   $229.40  
  Purchase #4 $51.96   5.482%   $54.8084   $54.81   $54.80   $54.80  
  Purchase #5 $16.57   7.339%   $17.7861   $17.79   $17.80   $17.80  
  Purchase #6 $157.63   3.736%   $163.5191   $163.52   $163.50   $163.50  
  Purchase #7 $239.29   9.478%   $261.9699   $261.97   $261.95   $262.00  
  7 purchase totals = $1,001.27       $1,095.0485   $1,095.05   $1,095.00   $1,095.00