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 $195.35   5.834%   $206.7467   $206.75   $206.75   $206.70  
  Purchase #2 $172.72   11.713%   $192.9507   $192.95   $192.95   $193.00  
  Purchase #3 $41.86   8.273%   $45.3231   $45.32   $45.30   $45.30  
  Purchase #4 $214.61   9.386%   $234.7533   $234.75   $234.75   $234.80  
  Purchase #5 $211.49   13.274%   $239.5632   $239.56   $239.55   $239.60  
  Purchase #6 $40.74   8.709%   $44.288   $44.29   $44.30   $44.30  
  Purchase #7 $215.25   11.391%   $239.7691   $239.77   $239.75   $239.80  
  7 purchase totals = $1,092.02       $1,203.3941   $1,203.39   $1,203.35   $1,203.50