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 $214.93   6.451%   $228.7951   $228.80   $228.80   $228.80  
  Purchase #2 $204.31   3.620%   $211.706   $211.71   $211.70   $211.70  
  Purchase #3 $24.70   10.399%   $27.2686   $27.27   $27.25   $27.30  
  Purchase #4 $58.26   11.279%   $64.8311   $64.83   $64.85   $64.80  
  Purchase #5 $39.67   10.126%   $43.687   $43.69   $43.70   $43.70  
  Purchase #6 $72.47   4.373%   $75.6391   $75.64   $75.65   $75.60  
  Purchase #7 $69.58   7.862%   $75.0504   $75.05   $75.05   $75.10  
  7 purchase totals = $683.92       $726.9773   $726.99   $727.00   $727.00