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 $82.31   5.123%   $86.5267   $86.53   $86.55   $86.50  
  Purchase #2 $214.71   11.784%   $240.0114   $240.01   $240.00   $240.00  
  Purchase #3 $24.27   5.465%   $25.5964   $25.60   $25.60   $25.60  
  Purchase #4 $250.95   10.143%   $276.4039   $276.40   $276.40   $276.40  
  Purchase #5 $19.95   10.163%   $21.9775   $21.98   $22.00   $22.00  
  Purchase #6 $174.51   5.381%   $183.9004   $183.90   $183.90   $183.90  
  Purchase #7 $231.42   12.256%   $259.7828   $259.78   $259.80   $259.80  
  7 purchase totals = $998.12       $1,094.1991   $1,094.20   $1,094.25   $1,094.20