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 $169.84   3.262%   $175.3802   $175.38   $175.40   $175.40  
  Purchase #2 $190.56   3.149%   $196.5607   $196.56   $196.55   $196.60  
  Purchase #3 $113.87   9.759%   $124.9826   $124.98   $125.00   $125.00  
  Purchase #4 $65.77   3.452%   $68.0404   $68.04   $68.05   $68.00  
  Purchase #5 $97.44   12.651%   $109.7671   $109.77   $109.75   $109.80  
  Purchase #6 $49.74   4.485%   $51.9708   $51.97   $51.95   $52.00  
  Purchase #7 $188.76   12.207%   $211.8019   $211.80   $211.80   $211.80  
  7 purchase totals = $875.98       $938.5037   $938.50   $938.50   $938.60