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 $211.81   7.163%   $226.982   $226.98   $227.00   $227.00  
  Purchase #2 $54.81   11.439%   $61.0797   $61.08   $61.10   $61.10  
  Purchase #3 $58.92   13.781%   $67.0398   $67.04   $67.05   $67.00  
  Purchase #4 $119.82   9.565%   $131.2808   $131.28   $131.30   $131.30  
  Purchase #5 $203.44   10.442%   $224.6832   $224.68   $224.70   $224.70  
  Purchase #6 $181.86   13.541%   $206.4857   $206.49   $206.50   $206.50  
  Purchase #7 $128.41   5.589%   $135.5868   $135.59   $135.60   $135.60  
  7 purchase totals = $959.07       $1,053.1380   $1,053.14   $1,053.25   $1,053.20