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 $227.35   8.651%   $247.018   $247.02   $247.00   $247.00  
  Purchase #2 $40.37   5.285%   $42.5036   $42.50   $42.50   $42.50  
  Purchase #3 $7.36   6.661%   $7.8502   $7.85   $7.85   $7.90  
  Purchase #4 $203.90   8.412%   $221.0521   $221.05   $221.05   $221.10  
  Purchase #5 $61.47   3.415%   $63.5692   $63.57   $63.55   $63.60  
  Purchase #6 $55.46   11.166%   $61.6527   $61.65   $61.65   $61.70  
  Purchase #7 $114.45   8.331%   $123.9848   $123.98   $124.00   $124.00  
  7 purchase totals = $710.36       $767.6306   $767.62   $767.60   $767.80