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 $56.32   11.181%   $62.6171   $62.62   $62.60   $62.60  
  Purchase #2 $173.97   7.219%   $186.5289   $186.53   $186.55   $186.50  
  Purchase #3 $241.57   10.272%   $266.3841   $266.38   $266.40   $266.40  
  Purchase #4 $177.51   12.177%   $199.1254   $199.13   $199.15   $199.10  
  Purchase #5 $226.72   9.238%   $247.6644   $247.66   $247.65   $247.70  
  Purchase #6 $110.79   10.641%   $122.5792   $122.58   $122.60   $122.60  
  Purchase #7 $119.29   10.789%   $132.1602   $132.16   $132.15   $132.20  
  7 purchase totals = $1,106.17       $1,217.0593   $1,217.06   $1,217.10   $1,217.10