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 $176.64   5.801%   $186.8869   $186.89   $186.90   $186.90  
  Purchase #2 $245.91   9.452%   $269.1534   $269.15   $269.15   $269.20  
  Purchase #3 $171.42   9.847%   $188.2997   $188.30   $188.30   $188.30  
  Purchase #4 $42.27   11.801%   $47.2583   $47.26   $47.25   $47.30  
  Purchase #5 $245.86   8.415%   $266.5491   $266.55   $266.55   $266.50  
  Purchase #6 $227.82   10.843%   $252.5225   $252.52   $252.50   $252.50  
  Purchase #7 $153.99   7.630%   $165.7394   $165.74   $165.75   $165.70  
  7 purchase totals = $1,263.91       $1,376.4093   $1,376.41   $1,376.40   $1,376.40