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 $214.96   3.832%   $223.1973   $223.20   $223.20   $223.20  
  Purchase #2 $224.78   4.822%   $235.6189   $235.62   $235.60   $235.60  
  Purchase #3 $40.92   5.212%   $43.0528   $43.05   $43.05   $43.10  
  Purchase #4 $113.99   12.302%   $128.013   $128.01   $128.00   $128.00  
  Purchase #5 $203.33   11.494%   $226.7008   $226.70   $226.70   $226.70  
  Purchase #6 $141.53   4.773%   $148.2852   $148.29   $148.30   $148.30  
  Purchase #7 $240.82   7.116%   $257.9568   $257.96   $257.95   $258.00  
  7 purchase totals = $1,180.33       $1,262.8248   $1,262.83   $1,262.80   $1,262.90