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 $160.83   4.482%   $168.0384   $168.04   $168.05   $168.00  
  Purchase #2 $196.34   8.832%   $213.6807   $213.68   $213.70   $213.70  
  Purchase #3 $50.94   4.363%   $53.1625   $53.16   $53.15   $53.20  
  Purchase #4 $193.33   11.397%   $215.3638   $215.36   $215.35   $215.40  
  Purchase #5 $212.57   13.230%   $240.693   $240.69   $240.70   $240.70  
  Purchase #6 $91.48   3.281%   $94.4815   $94.48   $94.50   $94.50  
  Purchase #7 $209.56   4.384%   $218.7471   $218.75   $218.75   $218.70  
  7 purchase totals = $1,115.05       $1,204.1670   $1,204.16   $1,204.20   $1,204.20