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 $60.29   5.506%   $63.6096   $63.61   $63.60   $63.60  
  Purchase #2 $211.51   3.449%   $218.805   $218.81   $218.80   $218.80  
  Purchase #3 $14.65   6.266%   $15.568   $15.57   $15.55   $15.60  
  Purchase #4 $31.85   4.723%   $33.3543   $33.35   $33.35   $33.40  
  Purchase #5 $123.36   11.266%   $137.2577   $137.26   $137.25   $137.30  
  Purchase #6 $124.50   13.764%   $141.6362   $141.64   $141.65   $141.60  
  Purchase #7 $196.26   3.219%   $202.5776   $202.58   $202.60   $202.60  
  7 purchase totals = $762.42       $812.8084   $812.82   $812.80   $812.90