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 $176.91   10.805%   $196.0251   $196.03   $196.05   $196.00  
  Purchase #2 $111.66   7.469%   $119.9999   $120.00   $120.00   $120.00  
  Purchase #3 $242.78   11.470%   $270.6269   $270.63   $270.65   $270.60  
  Purchase #4 $230.47   10.170%   $253.9088   $253.91   $253.90   $253.90  
  Purchase #5 $142.37   6.593%   $151.7565   $151.76   $151.75   $151.80  
  Purchase #6 $130.31   11.468%   $145.254   $145.25   $145.25   $145.30  
  Purchase #7 $73.42   4.515%   $76.7349   $76.73   $76.75   $76.70  
  7 purchase totals = $1,107.92       $1,214.3061   $1,214.31   $1,214.35   $1,214.30