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 $62.93   6.831%   $67.2287   $67.23   $67.25   $67.20  
  Purchase #2 $221.64   13.314%   $251.1491   $251.15   $251.15   $251.10  
  Purchase #3 $226.86   12.221%   $254.5846   $254.58   $254.60   $254.60  
  Purchase #4 $171.47   6.144%   $182.0051   $182.01   $182.00   $182.00  
  Purchase #5 $86.56   13.417%   $98.1738   $98.17   $98.15   $98.20  
  Purchase #6 $205.99   5.572%   $217.4678   $217.47   $217.45   $217.50  
  Purchase #7 $199.41   6.468%   $212.3078   $212.31   $212.30   $212.30  
  7 purchase totals = $1,174.86       $1,282.9169   $1,282.92   $1,282.90   $1,282.90