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 $92.52   3.379%   $95.6463   $95.65   $95.65   $95.60  
  Purchase #2 $158.36   6.730%   $169.0176   $169.02   $169.00   $169.00  
  Purchase #3 $167.52   5.297%   $176.3935   $176.39   $176.40   $176.40  
  Purchase #4 $110.72   13.843%   $126.047   $126.05   $126.05   $126.00  
  Purchase #5 $133.41   10.648%   $147.6155   $147.62   $147.60   $147.60  
  Purchase #6 $130.51   3.677%   $135.3089   $135.31   $135.30   $135.30  
  Purchase #7 $82.74   9.525%   $90.621   $90.62   $90.60   $90.60  
  7 purchase totals = $875.78       $940.6498   $940.66   $940.60   $940.50