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 $62.36   13.768%   $70.9457   $70.95   $70.95   $70.90  
  Purchase #2 $212.64   10.818%   $235.6434   $235.64   $235.65   $235.60  
  Purchase #3 $151.54   10.163%   $166.941   $166.94   $166.95   $166.90  
  Purchase #4 $217.55   4.718%   $227.814   $227.81   $227.80   $227.80  
  Purchase #5 $12.26   4.834%   $12.8526   $12.85   $12.85   $12.90  
  Purchase #6 $201.91   10.784%   $223.684   $223.68   $223.70   $223.70  
  Purchase #7 $116.31   11.632%   $129.8392   $129.84   $129.85   $129.80  
  7 purchase totals = $974.57       $1,067.7199   $1,067.71   $1,067.75   $1,067.60