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 $152.96   10.666%   $169.2747   $169.27   $169.25   $169.30  
  Purchase #2 $179.34   10.761%   $198.6388   $198.64   $198.65   $198.60  
  Purchase #3 $184.98   7.498%   $198.8498   $198.85   $198.85   $198.80  
  Purchase #4 $42.49   4.174%   $44.2635   $44.26   $44.25   $44.30  
  Purchase #5 $94.54   13.863%   $107.6461   $107.65   $107.65   $107.60  
  Purchase #6 $168.73   7.679%   $181.6868   $181.69   $181.70   $181.70  
  Purchase #7 $175.91   11.579%   $196.2786   $196.28   $196.30   $196.30  
  7 purchase totals = $998.95       $1,096.6383   $1,096.64   $1,096.65   $1,096.60