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 $116.33   13.492%   $132.0252   $132.03   $132.05   $132.00  
  Purchase #2 $103.55   12.377%   $116.3664   $116.37   $116.35   $116.40  
  Purchase #3 $135.66   4.679%   $142.0075   $142.01   $142.00   $142.00  
  Purchase #4 $204.57   3.713%   $212.1657   $212.17   $212.15   $212.20  
  Purchase #5 $85.75   4.378%   $89.5041   $89.50   $89.50   $89.50  
  Purchase #6 $245.88   7.787%   $265.0267   $265.03   $265.05   $265.00  
  Purchase #7 $214.76   11.710%   $239.9084   $239.91   $239.90   $239.90  
  7 purchase totals = $1,106.50       $1,197.0040   $1,197.02   $1,197.00   $1,197.00