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 $152.73   9.663%   $167.4883   $167.49   $167.50   $167.50  
  Purchase #2 $242.67   11.111%   $269.6331   $269.63   $269.65   $269.60  
  Purchase #3 $73.44   13.259%   $83.1774   $83.18   $83.20   $83.20  
  Purchase #4 $247.82   11.605%   $276.5795   $276.58   $276.60   $276.60  
  Purchase #5 $236.83   4.352%   $247.1368   $247.14   $247.15   $247.10  
  Purchase #6 $173.95   7.272%   $186.5996   $186.60   $186.60   $186.60  
  Purchase #7 $180.95   8.176%   $195.7445   $195.74   $195.75   $195.70  
  7 purchase totals = $1,308.39       $1,426.3592   $1,426.36   $1,426.45   $1,426.30