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 $44.51   5.244%   $46.8441   $46.84   $46.85   $46.80  
  Purchase #2 $218.56   11.300%   $243.2573   $243.26   $243.25   $243.30  
  Purchase #3 $183.54   5.581%   $193.7834   $193.78   $193.80   $193.80  
  Purchase #4 $181.53   11.575%   $202.5421   $202.54   $202.55   $202.50  
  Purchase #5 $38.79   12.551%   $43.6585   $43.66   $43.65   $43.70  
  Purchase #6 $244.33   10.243%   $269.3567   $269.36   $269.35   $269.40  
  Purchase #7 $249.73   9.524%   $273.5143   $273.51   $273.50   $273.50  
  7 purchase totals = $1,160.99       $1,272.9564   $1,272.95   $1,272.95   $1,273.00