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 $212.81   11.831%   $237.9876   $237.99   $238.00   $238.00  
  Purchase #2 $156.83   11.712%   $175.1979   $175.20   $175.20   $175.20  
  Purchase #3 $188.41   7.353%   $202.2638   $202.26   $202.25   $202.30  
  Purchase #4 $48.26   3.218%   $49.813   $49.81   $49.80   $49.80  
  Purchase #5 $183.35   4.217%   $191.0819   $191.08   $191.10   $191.10  
  Purchase #6 $59.74   8.175%   $64.6237   $64.62   $64.60   $64.60  
  Purchase #7 $85.74   9.485%   $93.8724   $93.87   $93.85   $93.90  
  7 purchase totals = $935.14       $1,014.8403   $1,014.83   $1,014.80   $1,014.90