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 $56.58   12.809%   $63.8273   $63.83   $63.85   $63.80  
  Purchase #2 $180.26   8.830%   $196.177   $196.18   $196.20   $196.20  
  Purchase #3 $59.82   3.591%   $61.9681   $61.97   $61.95   $62.00  
  Purchase #4 $183.67   5.510%   $193.7902   $193.79   $193.80   $193.80  
  Purchase #5 $183.57   13.102%   $207.6213   $207.62   $207.60   $207.60  
  Purchase #6 $184.65   5.572%   $194.9387   $194.94   $194.95   $194.90  
  Purchase #7 $113.98   11.871%   $127.5106   $127.51   $127.50   $127.50  
  7 purchase totals = $962.53       $1,045.8332   $1,045.84   $1,045.85   $1,045.80