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 $66.72   4.367%   $69.6337   $69.63   $69.65   $69.60  
  Purchase #2 $240.25   4.608%   $251.3207   $251.32   $251.30   $251.30  
  Purchase #3 $102.70   13.808%   $116.8808   $116.88   $116.90   $116.90  
  Purchase #4 $229.28   5.802%   $242.5828   $242.58   $242.60   $242.60  
  Purchase #5 $198.55   4.575%   $207.6337   $207.63   $207.65   $207.60  
  Purchase #6 $43.68   5.154%   $45.9313   $45.93   $45.95   $45.90  
  Purchase #7 $123.85   3.450%   $128.1228   $128.12   $128.10   $128.10  
  7 purchase totals = $1,005.03       $1,062.1058   $1,062.09   $1,062.15   $1,062.00