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 $133.52   10.807%   $147.9495   $147.95   $147.95   $147.90  
  Purchase #2 $86.52   9.191%   $94.4721   $94.47   $94.45   $94.50  
  Purchase #3 $176.55   10.627%   $195.312   $195.31   $195.30   $195.30  
  Purchase #4 $75.26   5.778%   $79.6085   $79.61   $79.60   $79.60  
  Purchase #5 $237.47   13.256%   $268.949   $268.95   $268.95   $268.90  
  Purchase #6 $204.61   11.594%   $228.3325   $228.33   $228.35   $228.30  
  Purchase #7 $227.43   5.280%   $239.4383   $239.44   $239.45   $239.40  
  7 purchase totals = $1,141.36       $1,254.0619   $1,254.06   $1,254.05   $1,253.90