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 $168.73   3.814%   $175.1654   $175.17   $175.15   $175.20  
  Purchase #2 $120.33   10.169%   $132.5664   $132.57   $132.55   $132.60  
  Purchase #3 $244.66   7.837%   $263.834   $263.83   $263.85   $263.80  
  Purchase #4 $74.49   4.341%   $77.7236   $77.72   $77.70   $77.70  
  Purchase #5 $176.25   3.290%   $182.0486   $182.05   $182.05   $182.00  
  Purchase #6 $116.50   4.252%   $121.4536   $121.45   $121.45   $121.50  
  Purchase #7 $55.72   5.241%   $58.6403   $58.64   $58.65   $58.60  
  7 purchase totals = $956.68       $1,011.4319   $1,011.43   $1,011.40   $1,011.40