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 $211.60   11.524%   $235.9848   $235.98   $236.00   $236.00  
  Purchase #2 $171.51   7.104%   $183.6941   $183.69   $183.70   $183.70  
  Purchase #3 $16.40   3.298%   $16.9409   $16.94   $16.95   $16.90  
  Purchase #4 $108.69   13.534%   $123.4001   $123.40   $123.40   $123.40  
  Purchase #5 $112.96   8.267%   $122.2984   $122.30   $122.30   $122.30  
  Purchase #6 $155.54   4.489%   $162.5222   $162.52   $162.50   $162.50  
  Purchase #7 $197.65   9.251%   $215.9346   $215.93   $215.95   $215.90  
  7 purchase totals = $974.35       $1,060.7751   $1,060.76   $1,060.80   $1,060.70