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 $188.55   13.523%   $214.0476   $214.05   $214.05   $214.00  
  Purchase #2 $86.51   8.702%   $94.0381   $94.04   $94.05   $94.00  
  Purchase #3 $149.26   10.831%   $165.4264   $165.43   $165.45   $165.40  
  Purchase #4 $61.44   11.714%   $68.6371   $68.64   $68.65   $68.60  
  Purchase #5 $223.30   4.301%   $232.9041   $232.90   $232.90   $232.90  
  Purchase #6 $214.93   10.553%   $237.6116   $237.61   $237.60   $237.60  
  Purchase #7 $238.29   3.852%   $247.4689   $247.47   $247.45   $247.50  
  7 purchase totals = $1,162.28       $1,260.1338   $1,260.14   $1,260.15   $1,260.00