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 $86.37   9.515%   $94.5881   $94.59   $94.60   $94.60  
  Purchase #2 $246.75   10.547%   $272.7747   $272.77   $272.75   $272.80  
  Purchase #3 $216.83   8.636%   $235.5554   $235.56   $235.55   $235.60  
  Purchase #4 $168.37   9.489%   $184.3466   $184.35   $184.35   $184.30  
  Purchase #5 $62.41   8.247%   $67.557   $67.56   $67.55   $67.60  
  Purchase #6 $209.36   9.496%   $229.2408   $229.24   $229.25   $229.20  
  Purchase #7 $68.98   5.385%   $72.6946   $72.69   $72.70   $72.70  
  7 purchase totals = $1,059.07       $1,156.7572   $1,156.76   $1,156.75   $1,156.80