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 $88.65   7.400%   $95.2101   $95.21   $95.20   $95.20  
  Purchase #2 $195.72   7.373%   $210.1504   $210.15   $210.15   $210.20  
  Purchase #3 $79.94   6.451%   $85.0969   $85.10   $85.10   $85.10  
  Purchase #4 $213.86   8.274%   $231.5548   $231.55   $231.55   $231.60  
  Purchase #5 $52.42   4.469%   $54.7626   $54.76   $54.75   $54.80  
  Purchase #6 $237.50   7.195%   $254.5881   $254.59   $254.60   $254.60  
  Purchase #7 $124.81   6.644%   $133.1024   $133.10   $133.10   $133.10  
  7 purchase totals = $992.90       $1,064.4653   $1,064.46   $1,064.45   $1,064.60