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 $171.54   13.851%   $195.3   $195.30   $195.30   $195.30  
  Purchase #2 $240.53   5.507%   $253.776   $253.78   $253.80   $253.80  
  Purchase #3 $183.47   4.793%   $192.2637   $192.26   $192.25   $192.30  
  Purchase #4 $111.91   8.488%   $121.4089   $121.41   $121.40   $121.40  
  Purchase #5 $191.29   10.801%   $211.9512   $211.95   $211.95   $212.00  
  Purchase #6 $127.54   5.163%   $134.1249   $134.12   $134.10   $134.10  
  Purchase #7 $167.58   10.649%   $185.4256   $185.43   $185.45   $185.40  
  7 purchase totals = $1,193.86       $1,294.2503   $1,294.25   $1,294.25   $1,294.30