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 $61.50   9.656%   $67.4384   $67.44   $67.45   $67.40  
  Purchase #2 $202.43   12.549%   $227.8329   $227.83   $227.85   $227.80  
  Purchase #3 $129.65   5.689%   $137.0258   $137.03   $137.05   $137.00  
  Purchase #4 $85.44   5.293%   $89.9623   $89.96   $89.95   $90.00  
  Purchase #5 $58.65   4.110%   $61.0605   $61.06   $61.05   $61.10  
  Purchase #6 $230.87   8.633%   $250.801   $250.80   $250.80   $250.80  
  Purchase #7 $160.27   10.428%   $176.983   $176.98   $177.00   $177.00  
  7 purchase totals = $928.81       $1,011.1039   $1,011.10   $1,011.15   $1,011.10