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 $196.75   8.591%   $213.6528   $213.65   $213.65   $213.70  
  Purchase #2 $160.41   10.555%   $177.3413   $177.34   $177.35   $177.30  
  Purchase #3 $152.41   13.538%   $173.0433   $173.04   $173.05   $173.00  
  Purchase #4 $86.86   3.784%   $90.1468   $90.15   $90.15   $90.10  
  Purchase #5 $56.67   11.417%   $63.14   $63.14   $63.15   $63.10  
  Purchase #6 $243.84   11.533%   $271.9621   $271.96   $271.95   $272.00  
  Purchase #7 $122.77   10.663%   $135.861   $135.86   $135.85   $135.90  
  7 purchase totals = $1,019.71       $1,125.1473   $1,125.14   $1,125.15   $1,125.10