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 $58.74   4.628%   $61.4585   $61.46   $61.45   $61.50  
  Purchase #2 $94.54   13.554%   $107.354   $107.35   $107.35   $107.40  
  Purchase #3 $116.52   4.192%   $121.4045   $121.40   $121.40   $121.40  
  Purchase #4 $236.56   3.386%   $244.5699   $244.57   $244.55   $244.60  
  Purchase #5 $231.59   4.432%   $241.8541   $241.85   $241.85   $241.90  
  Purchase #6 $196.38   9.134%   $214.3173   $214.32   $214.30   $214.30  
  Purchase #7 $171.35   8.565%   $186.0261   $186.03   $186.05   $186.00  
  7 purchase totals = $1,105.68       $1,176.9844   $1,176.98   $1,176.95   $1,177.10