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 $192.69   4.749%   $201.8408   $201.84   $201.85   $201.80  
  Purchase #2 $32.39   8.608%   $35.1781   $35.18   $35.20   $35.20  
  Purchase #3 $214.88   3.521%   $222.4459   $222.45   $222.45   $222.40  
  Purchase #4 $103.86   11.234%   $115.5276   $115.53   $115.55   $115.50  
  Purchase #5 $146.41   4.859%   $153.5241   $153.52   $153.50   $153.50  
  Purchase #6 $72.79   4.690%   $76.2039   $76.20   $76.20   $76.20  
  Purchase #7 $123.31   7.331%   $132.3499   $132.35   $132.35   $132.30  
  7 purchase totals = $886.33       $937.0703   $937.07   $937.10   $936.90