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 $41.61   11.310%   $46.3161   $46.32   $46.30   $46.30  
  Purchase #2 $169.61   12.651%   $191.0674   $191.07   $191.05   $191.10  
  Purchase #3 $57.50   12.716%   $64.8117   $64.81   $64.80   $64.80  
  Purchase #4 $243.91   6.639%   $260.1032   $260.10   $260.10   $260.10  
  Purchase #5 $74.88   6.114%   $79.4582   $79.46   $79.45   $79.50  
  Purchase #6 $219.75   9.605%   $240.857   $240.86   $240.85   $240.90  
  Purchase #7 $167.69   11.181%   $186.4394   $186.44   $186.45   $186.40  
  7 purchase totals = $974.95       $1,069.0530   $1,069.06   $1,069.00   $1,069.10