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 $175.52   6.463%   $186.8639   $186.86   $186.85   $186.90  
  Purchase #2 $41.41   4.444%   $43.2503   $43.25   $43.25   $43.30  
  Purchase #3 $109.41   8.827%   $119.0676   $119.07   $119.05   $119.10  
  Purchase #4 $47.78   4.150%   $49.7629   $49.76   $49.75   $49.80  
  Purchase #5 $95.84   6.743%   $102.3025   $102.30   $102.30   $102.30  
  Purchase #6 $193.69   12.369%   $217.6475   $217.65   $217.65   $217.60  
  Purchase #7 $33.59   8.794%   $36.5439   $36.54   $36.55   $36.50  
  7 purchase totals = $697.24       $755.4386   $755.43   $755.40   $755.50