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 $208.32   7.412%   $223.7607   $223.76   $223.75   $223.80  
  Purchase #2 $220.45   8.578%   $239.3602   $239.36   $239.35   $239.40  
  Purchase #3 $212.58   7.524%   $228.5745   $228.57   $228.55   $228.60  
  Purchase #4 $119.26   7.739%   $128.4895   $128.49   $128.50   $128.50  
  Purchase #5 $188.49   7.508%   $202.6418   $202.64   $202.65   $202.60  
  Purchase #6 $228.36   11.357%   $254.2948   $254.29   $254.30   $254.30  
  Purchase #7 $53.88   3.774%   $55.9134   $55.91   $55.90   $55.90  
  7 purchase totals = $1,231.34       $1,333.0349   $1,333.02   $1,333.00   $1,333.10