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 $54.46   13.860%   $62.0082   $62.01   $62.00   $62.00  
  Purchase #2 $211.29   3.640%   $218.981   $218.98   $219.00   $219.00  
  Purchase #3 $97.39   4.603%   $101.8729   $101.87   $101.85   $101.90  
  Purchase #4 $173.73   9.618%   $190.4394   $190.44   $190.45   $190.40  
  Purchase #5 $113.58   3.119%   $117.1226   $117.12   $117.10   $117.10  
  Purchase #6 $28.71   9.106%   $31.3243   $31.32   $31.30   $31.30  
  Purchase #7 $156.81   4.854%   $164.4216   $164.42   $164.40   $164.40  
  7 purchase totals = $835.97       $886.1700   $886.16   $886.10   $886.10