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 $59.65   3.849%   $61.9459   $61.95   $61.95   $61.90  
  Purchase #2 $247.50   13.805%   $281.6674   $281.67   $281.65   $281.70  
  Purchase #3 $175.84   13.528%   $199.6276   $199.63   $199.65   $199.60  
  Purchase #4 $18.25   6.384%   $19.4151   $19.42   $19.40   $19.40  
  Purchase #5 $197.71   4.289%   $206.1898   $206.19   $206.20   $206.20  
  Purchase #6 $160.62   12.663%   $180.9593   $180.96   $180.95   $181.00  
  Purchase #7 $64.42   10.299%   $71.0546   $71.05   $71.05   $71.10  
  7 purchase totals = $923.99       $1,020.8597   $1,020.87   $1,020.85   $1,020.90