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 $196.79   8.562%   $213.6392   $213.64   $213.65   $213.60  
  Purchase #2 $202.86   5.726%   $214.4758   $214.48   $214.50   $214.50  
  Purchase #3 $132.50   11.431%   $147.6461   $147.65   $147.65   $147.60  
  Purchase #4 $52.77   6.621%   $56.2639   $56.26   $56.25   $56.30  
  Purchase #5 $162.53   9.717%   $178.323   $178.32   $178.30   $178.30  
  Purchase #6 $87.61   13.848%   $99.7422   $99.74   $99.75   $99.70  
  Purchase #7 $236.89   8.605%   $257.2744   $257.27   $257.25   $257.30  
  7 purchase totals = $1,071.95       $1,167.3646   $1,167.36   $1,167.35   $1,167.30