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 $192.54   3.365%   $199.019   $199.02   $199.00   $199.00  
  Purchase #2 $161.41   6.448%   $171.8177   $171.82   $171.80   $171.80  
  Purchase #3 $167.39   7.623%   $180.1501   $180.15   $180.15   $180.20  
  Purchase #4 $122.39   11.675%   $136.679   $136.68   $136.70   $136.70  
  Purchase #5 $148.29   4.640%   $155.1707   $155.17   $155.15   $155.20  
  Purchase #6 $238.27   4.332%   $248.5919   $248.59   $248.60   $248.60  
  Purchase #7 $183.76   11.182%   $204.308   $204.31   $204.30   $204.30  
  7 purchase totals = $1,214.05       $1,295.7364   $1,295.74   $1,295.70   $1,295.80