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 $183.52   7.814%   $197.8603   $197.86   $197.85   $197.90  
  Purchase #2 $171.48   8.356%   $185.8089   $185.81   $185.80   $185.80  
  Purchase #3 $15.38   7.132%   $16.4769   $16.48   $16.50   $16.50  
  Purchase #4 $219.57   12.694%   $247.4422   $247.44   $247.45   $247.40  
  Purchase #5 $125.60   8.819%   $136.6767   $136.68   $136.70   $136.70  
  Purchase #6 $97.41   7.839%   $105.046   $105.05   $105.05   $105.00  
  Purchase #7 $34.87   3.638%   $36.1386   $36.14   $36.15   $36.10  
  7 purchase totals = $847.83       $925.4496   $925.46   $925.50   $925.40