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 $41.40   11.245%   $46.0554   $46.06   $46.05   $46.10  
  Purchase #2 $240.43   11.252%   $267.4832   $267.48   $267.50   $267.50  
  Purchase #3 $174.75   10.758%   $193.5496   $193.55   $193.55   $193.50  
  Purchase #4 $195.48   4.380%   $204.042   $204.04   $204.05   $204.00  
  Purchase #5 $94.91   5.481%   $100.112   $100.11   $100.10   $100.10  
  Purchase #6 $137.43   7.384%   $147.5778   $147.58   $147.60   $147.60  
  Purchase #7 $249.79   13.393%   $283.2444   $283.24   $283.25   $283.20  
  7 purchase totals = $1,134.19       $1,242.0644   $1,242.06   $1,242.10   $1,242.00