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 $236.46   4.387%   $246.8335   $246.83   $246.85   $246.80  
  Purchase #2 $202.31   3.218%   $208.8203   $208.82   $208.80   $208.80  
  Purchase #3 $8.77   6.170%   $9.3111   $9.31   $9.30   $9.30  
  Purchase #4 $46.35   3.511%   $47.9773   $47.98   $48.00   $48.00  
  Purchase #5 $211.26   11.723%   $236.026   $236.03   $236.05   $236.00  
  Purchase #6 $193.93   6.511%   $206.5568   $206.56   $206.55   $206.60  
  Purchase #7 $189.79   3.521%   $196.4725   $196.47   $196.45   $196.50  
  7 purchase totals = $1,088.87       $1,151.9975   $1,152.00   $1,152.00   $1,152.00