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 $182.26   10.453%   $201.3116   $201.31   $201.30   $201.30  
  Purchase #2 $32.87   5.427%   $34.6539   $34.65   $34.65   $34.70  
  Purchase #3 $31.35   8.420%   $33.9897   $33.99   $34.00   $34.00  
  Purchase #4 $178.61   3.599%   $185.0382   $185.04   $185.05   $185.00  
  Purchase #5 $19.69   5.489%   $20.7708   $20.77   $20.75   $20.80  
  Purchase #6 $173.68   10.774%   $192.3923   $192.39   $192.40   $192.40  
  Purchase #7 $136.26   12.755%   $153.64   $153.64   $153.65   $153.60  
  7 purchase totals = $754.72       $821.7965   $821.79   $821.80   $821.80