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 $57.31   9.862%   $62.9619   $62.96   $62.95   $63.00  
  Purchase #2 $241.72   5.204%   $254.2991   $254.30   $254.30   $254.30  
  Purchase #3 $205.75   7.507%   $221.1957   $221.20   $221.20   $221.20  
  Purchase #4 $186.43   3.138%   $192.2802   $192.28   $192.30   $192.30  
  Purchase #5 $154.74   3.350%   $159.9238   $159.92   $159.90   $159.90  
  Purchase #6 $122.75   7.495%   $131.9501   $131.95   $131.95   $132.00  
  Purchase #7 $39.62   7.499%   $42.5911   $42.59   $42.60   $42.60  
  7 purchase totals = $1,008.32       $1,065.2019   $1,065.20   $1,065.20   $1,065.30