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 $224.52   13.332%   $254.453   $254.45   $254.45   $254.50  
  Purchase #2 $57.86   7.634%   $62.277   $62.28   $62.30   $62.30  
  Purchase #3 $225.32   3.279%   $232.7082   $232.71   $232.70   $232.70  
  Purchase #4 $219.50   4.777%   $229.9855   $229.99   $230.00   $230.00  
  Purchase #5 $65.75   7.203%   $70.486   $70.49   $70.50   $70.50  
  Purchase #6 $155.54   13.613%   $176.7137   $176.71   $176.70   $176.70  
  Purchase #7 $69.85   7.214%   $74.889   $74.89   $74.90   $74.90  
  7 purchase totals = $1,018.34       $1,101.5124   $1,101.52   $1,101.55   $1,101.60