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 $214.44   4.474%   $224.034   $224.03   $224.05   $224.00  
  Purchase #2 $145.78   9.760%   $160.0081   $160.01   $160.00   $160.00  
  Purchase #3 $13.62   8.274%   $14.7469   $14.75   $14.75   $14.70  
  Purchase #4 $245.62   6.294%   $261.0793   $261.08   $261.10   $261.10  
  Purchase #5 $145.58   6.651%   $155.2625   $155.26   $155.25   $155.30  
  Purchase #6 $177.57   7.614%   $191.0902   $191.09   $191.10   $191.10  
  Purchase #7 $160.52   9.809%   $176.2654   $176.27   $176.25   $176.30  
  7 purchase totals = $1,103.13       $1,182.4864   $1,182.49   $1,182.50   $1,182.50