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 $208.69   12.625%   $235.0371   $235.04   $235.05   $235.00  
  Purchase #2 $93.62   3.204%   $96.6196   $96.62   $96.60   $96.60  
  Purchase #3 $173.34   3.198%   $178.8834   $178.88   $178.90   $178.90  
  Purchase #4 $53.92   3.702%   $55.9161   $55.92   $55.90   $55.90  
  Purchase #5 $49.56   5.627%   $52.3487   $52.35   $52.35   $52.30  
  Purchase #6 $57.99   5.263%   $61.042   $61.04   $61.05   $61.00  
  Purchase #7 $48.79   12.695%   $54.9839   $54.98   $55.00   $55.00  
  7 purchase totals = $685.91       $734.8308   $734.83   $734.85   $734.70