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 $161.68   7.716%   $174.1552   $174.16   $174.15   $174.20  
  Purchase #2 $174.87   6.789%   $186.7419   $186.74   $186.75   $186.70  
  Purchase #3 $204.31   9.417%   $223.5499   $223.55   $223.55   $223.50  
  Purchase #4 $109.97   6.212%   $116.8013   $116.80   $116.80   $116.80  
  Purchase #5 $54.70   6.870%   $58.4579   $58.46   $58.45   $58.50  
  Purchase #6 $234.48   9.297%   $256.2796   $256.28   $256.30   $256.30  
  Purchase #7 $8.25   7.741%   $8.8886   $8.89   $8.90   $8.90  
  7 purchase totals = $948.26       $1,024.8744   $1,024.88   $1,024.90   $1,024.90