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 $185.68   5.347%   $195.6083   $195.61   $195.60   $195.60  
  Purchase #2 $245.28   13.204%   $277.6668   $277.67   $277.65   $277.70  
  Purchase #3 $23.83   10.532%   $26.3398   $26.34   $26.35   $26.30  
  Purchase #4 $188.46   10.723%   $208.6686   $208.67   $208.65   $208.70  
  Purchase #5 $22.53   5.379%   $23.7419   $23.74   $23.75   $23.70  
  Purchase #6 $189.25   7.148%   $202.7776   $202.78   $202.80   $202.80  
  Purchase #7 $183.51   4.723%   $192.1772   $192.18   $192.20   $192.20  
  7 purchase totals = $1,038.54       $1,126.9802   $1,126.99   $1,127.00   $1,127.00