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 $219.28   11.124%   $243.6727   $243.67   $243.65   $243.70  
  Purchase #2 $174.95   11.839%   $195.6623   $195.66   $195.65   $195.70  
  Purchase #3 $89.39   4.171%   $93.1185   $93.12   $93.10   $93.10  
  Purchase #4 $220.78   7.127%   $236.515   $236.52   $236.50   $236.50  
  Purchase #5 $165.91   8.697%   $180.3392   $180.34   $180.35   $180.30  
  Purchase #6 $208.52   9.548%   $228.4295   $228.43   $228.45   $228.40  
  Purchase #7 $58.83   13.262%   $66.632   $66.63   $66.65   $66.60  
  7 purchase totals = $1,137.66       $1,244.3692   $1,244.37   $1,244.35   $1,244.30