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 $91.36   4.728%   $95.6795   $95.68   $95.70   $95.70  
  Purchase #2 $210.86   12.718%   $237.6772   $237.68   $237.70   $237.70  
  Purchase #3 $6.91   5.514%   $7.291   $7.29   $7.30   $7.30  
  Purchase #4 $141.30   4.574%   $147.7631   $147.76   $147.75   $147.80  
  Purchase #5 $151.36   13.288%   $171.4727   $171.47   $171.45   $171.50  
  Purchase #6 $159.92   9.647%   $175.3475   $175.35   $175.35   $175.30  
  Purchase #7 $227.90   12.195%   $255.6924   $255.69   $255.70   $255.70  
  7 purchase totals = $989.61       $1,090.9234   $1,090.92   $1,090.95   $1,091.00