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 $44.40   7.330%   $47.6545   $47.65   $47.65   $47.70  
  Purchase #2 $164.61   11.812%   $184.0537   $184.05   $184.05   $184.10  
  Purchase #3 $244.30   9.760%   $268.1437   $268.14   $268.15   $268.10  
  Purchase #4 $221.43   8.177%   $239.5363   $239.54   $239.55   $239.50  
  Purchase #5 $218.79   6.603%   $233.2367   $233.24   $233.25   $233.20  
  Purchase #6 $87.42   9.327%   $95.5737   $95.57   $95.55   $95.60  
  Purchase #7 $112.60   10.104%   $123.9771   $123.98   $124.00   $124.00  
  7 purchase totals = $1,093.55       $1,192.1757   $1,192.17   $1,192.20   $1,192.20