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 $152.61   6.657%   $162.7692   $162.77   $162.75   $162.80  
  Purchase #2 $207.37   5.743%   $219.2793   $219.28   $219.30   $219.30  
  Purchase #3 $9.88   5.155%   $10.3893   $10.39   $10.40   $10.40  
  Purchase #4 $152.57   3.149%   $157.3744   $157.37   $157.35   $157.40  
  Purchase #5 $164.89   5.245%   $173.5385   $173.54   $173.55   $173.50  
  Purchase #6 $237.82   3.784%   $246.8191   $246.82   $246.80   $246.80  
  Purchase #7 $101.55   4.739%   $106.3625   $106.36   $106.35   $106.40  
  7 purchase totals = $1,026.69       $1,076.5323   $1,076.53   $1,076.50   $1,076.60