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 $182.66   5.347%   $192.4268   $192.43   $192.45   $192.40  
  Purchase #2 $186.63   13.207%   $211.2782   $211.28   $211.30   $211.30  
  Purchase #3 $22.82   8.510%   $24.762   $24.76   $24.75   $24.80  
  Purchase #4 $166.67   6.422%   $177.3735   $177.37   $177.35   $177.40  
  Purchase #5 $170.66   6.543%   $181.8263   $181.83   $181.85   $181.80  
  Purchase #6 $121.88   12.386%   $136.9761   $136.98   $137.00   $137.00  
  Purchase #7 $163.30   12.316%   $183.412   $183.41   $183.40   $183.40  
  7 purchase totals = $1,014.62       $1,108.0549   $1,108.06   $1,108.10   $1,108.10