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 $204.31   7.568%   $219.7722   $219.77   $219.75   $219.80  
  Purchase #2 $127.29   11.328%   $141.7094   $141.71   $141.70   $141.70  
  Purchase #3 $40.35   9.503%   $44.1845   $44.18   $44.20   $44.20  
  Purchase #4 $163.69   3.523%   $169.4568   $169.46   $169.45   $169.50  
  Purchase #5 $41.82   4.842%   $43.8449   $43.84   $43.85   $43.80  
  Purchase #6 $211.97   12.275%   $237.9893   $237.99   $238.00   $238.00  
  Purchase #7 $175.25   9.758%   $192.3509   $192.35   $192.35   $192.40  
  7 purchase totals = $964.68       $1,049.3080   $1,049.30   $1,049.30   $1,049.40