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 $62.90   7.736%   $67.7659   $67.77   $67.75   $67.80  
  Purchase #2 $226.79   9.644%   $248.6616   $248.66   $248.65   $248.70  
  Purchase #3 $41.39   13.341%   $46.9118   $46.91   $46.90   $46.90  
  Purchase #4 $191.58   5.549%   $202.2108   $202.21   $202.20   $202.20  
  Purchase #5 $130.76   3.184%   $134.9234   $134.92   $134.90   $134.90  
  Purchase #6 $185.67   3.776%   $192.6809   $192.68   $192.70   $192.70  
  Purchase #7 $159.29   9.336%   $174.1613   $174.16   $174.15   $174.20  
  7 purchase totals = $998.38       $1,067.3157   $1,067.31   $1,067.25   $1,067.40