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 $42.95   3.284%   $44.3605   $44.36   $44.35   $44.40  
  Purchase #2 $193.27   13.582%   $219.5199   $219.52   $219.50   $219.50  
  Purchase #3 $162.64   8.779%   $176.9182   $176.92   $176.90   $176.90  
  Purchase #4 $169.26   4.577%   $177.007   $177.01   $177.00   $177.00  
  Purchase #5 $215.91   5.464%   $227.7073   $227.71   $227.70   $227.70  
  Purchase #6 $178.36   13.442%   $202.3352   $202.34   $202.35   $202.30  
  Purchase #7 $230.31   10.462%   $254.405   $254.41   $254.40   $254.40  
  7 purchase totals = $1,192.70       $1,302.2531   $1,302.27   $1,302.20   $1,302.20