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 $68.87   6.176%   $73.1234   $73.12   $73.10   $73.10  
  Purchase #2 $13.97   5.216%   $14.6987   $14.70   $14.70   $14.70  
  Purchase #3 $54.49   12.131%   $61.1002   $61.10   $61.10   $61.10  
  Purchase #4 $241.52   8.602%   $262.2956   $262.30   $262.30   $262.30  
  Purchase #5 $208.82   11.819%   $233.5004   $233.50   $233.50   $233.50  
  Purchase #6 $207.43   5.717%   $219.2888   $219.29   $219.30   $219.30  
  Purchase #7 $187.88   5.781%   $198.7413   $198.74   $198.75   $198.70  
  7 purchase totals = $982.98       $1,062.7484   $1,062.75   $1,062.75   $1,062.70