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 $83.89   12.748%   $94.5843   $94.58   $94.60   $94.60  
  Purchase #2 $203.43   12.467%   $228.7916   $228.79   $228.80   $228.80  
  Purchase #3 $54.93   4.840%   $57.5886   $57.59   $57.60   $57.60  
  Purchase #4 $183.59   5.196%   $193.1293   $193.13   $193.15   $193.10  
  Purchase #5 $150.44   7.491%   $161.7095   $161.71   $161.70   $161.70  
  Purchase #6 $33.41   3.299%   $34.5122   $34.51   $34.50   $34.50  
  Purchase #7 $95.38   9.731%   $104.6614   $104.66   $104.65   $104.70  
  7 purchase totals = $805.07       $874.9769   $874.97   $875.00   $875.00