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 $63.36   10.439%   $69.9742   $69.97   $69.95   $70.00  
  Purchase #2 $208.45   12.147%   $233.7704   $233.77   $233.75   $233.80  
  Purchase #3 $235.68   11.189%   $262.0502   $262.05   $262.05   $262.10  
  Purchase #4 $108.55   10.411%   $119.8511   $119.85   $119.85   $119.90  
  Purchase #5 $5.95   9.759%   $6.5307   $6.53   $6.55   $6.50  
  Purchase #6 $238.88   13.547%   $271.2411   $271.24   $271.25   $271.20  
  Purchase #7 $49.71   7.755%   $53.565   $53.57   $53.55   $53.60  
  7 purchase totals = $910.58       $1,016.9827   $1,016.98   $1,016.95   $1,017.10