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 $68.31   9.345%   $74.6936   $74.69   $74.70   $74.70  
  Purchase #2 $117.96   6.591%   $125.7347   $125.73   $125.75   $125.70  
  Purchase #3 $72.84   10.738%   $80.6616   $80.66   $80.65   $80.70  
  Purchase #4 $75.34   4.397%   $78.6527   $78.65   $78.65   $78.70  
  Purchase #5 $170.82   11.839%   $191.0434   $191.04   $191.05   $191.00  
  Purchase #6 $233.27   3.652%   $241.789   $241.79   $241.80   $241.80  
  Purchase #7 $195.86   12.151%   $219.6589   $219.66   $219.65   $219.70  
  7 purchase totals = $934.40       $1,012.2339   $1,012.22   $1,012.25   $1,012.30