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 $208.75   7.380%   $224.1558   $224.16   $224.15   $224.20  
  Purchase #2 $87.46   5.548%   $92.3123   $92.31   $92.30   $92.30  
  Purchase #3 $237.40   6.483%   $252.7906   $252.79   $252.80   $252.80  
  Purchase #4 $246.69   6.557%   $262.8655   $262.87   $262.85   $262.90  
  Purchase #5 $221.57   4.268%   $231.0266   $231.03   $231.05   $231.00  
  Purchase #6 $166.74   7.145%   $178.6536   $178.65   $178.65   $178.70  
  Purchase #7 $210.75   5.850%   $223.0789   $223.08   $223.10   $223.10  
  7 purchase totals = $1,379.36       $1,464.8833   $1,464.89   $1,464.90   $1,465.00