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 $126.77   5.783%   $134.1011   $134.10   $134.10   $134.10  
  Purchase #2 $140.71   4.720%   $147.3515   $147.35   $147.35   $147.40  
  Purchase #3 $30.84   9.398%   $33.7383   $33.74   $33.75   $33.70  
  Purchase #4 $185.69   4.631%   $194.2893   $194.29   $194.30   $194.30  
  Purchase #5 $192.36   13.469%   $218.269   $218.27   $218.25   $218.30  
  Purchase #6 $23.87   8.785%   $25.967   $25.97   $25.95   $26.00  
  Purchase #7 $108.42   13.472%   $123.0263   $123.03   $123.05   $123.00  
  7 purchase totals = $808.66       $876.7425   $876.75   $876.75   $876.80