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 $91.90   4.122%   $95.6881   $95.69   $95.70   $95.70  
  Purchase #2 $162.57   12.487%   $182.8701   $182.87   $182.85   $182.90  
  Purchase #3 $195.32   6.844%   $208.6877   $208.69   $208.70   $208.70  
  Purchase #4 $152.67   6.467%   $162.5432   $162.54   $162.55   $162.50  
  Purchase #5 $101.85   4.748%   $106.6858   $106.69   $106.70   $106.70  
  Purchase #6 $150.84   6.713%   $160.9659   $160.97   $160.95   $161.00  
  Purchase #7 $30.59   11.568%   $34.1287   $34.13   $34.15   $34.10  
  7 purchase totals = $885.74       $951.5695   $951.58   $951.60   $951.60