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 $62.85   9.286%   $68.6863   $68.69   $68.70   $68.70  
  Purchase #2 $206.82   4.767%   $216.6791   $216.68   $216.70   $216.70  
  Purchase #3 $31.61   6.191%   $33.567   $33.57   $33.55   $33.60  
  Purchase #4 $77.44   3.836%   $80.4106   $80.41   $80.40   $80.40  
  Purchase #5 $171.63   4.540%   $179.422   $179.42   $179.40   $179.40  
  Purchase #6 $224.54   5.842%   $237.6576   $237.66   $237.65   $237.70  
  Purchase #7 $175.79   11.405%   $195.8388   $195.84   $195.85   $195.80  
  7 purchase totals = $950.68       $1,012.2614   $1,012.27   $1,012.25   $1,012.30