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 $99.95   7.676%   $107.6222   $107.62   $107.60   $107.60  
  Purchase #2 $175.65   11.123%   $195.1875   $195.19   $195.20   $195.20  
  Purchase #3 $66.25   3.191%   $68.364   $68.36   $68.35   $68.40  
  Purchase #4 $56.93   6.547%   $60.6572   $60.66   $60.65   $60.70  
  Purchase #5 $192.53   3.194%   $198.6794   $198.68   $198.70   $198.70  
  Purchase #6 $236.62   4.312%   $246.8231   $246.82   $246.80   $246.80  
  Purchase #7 $224.93   12.464%   $252.9653   $252.97   $252.95   $253.00  
  7 purchase totals = $1,052.86       $1,130.2987   $1,130.30   $1,130.25   $1,130.40