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 $209.52   12.614%   $235.9489   $235.95   $235.95   $235.90  
  Purchase #2 $224.73   8.158%   $243.0635   $243.06   $243.05   $243.10  
  Purchase #3 $212.79   6.624%   $226.8852   $226.89   $226.90   $226.90  
  Purchase #4 $47.70   12.797%   $53.8042   $53.80   $53.80   $53.80  
  Purchase #5 $244.60   8.730%   $265.9536   $265.95   $265.95   $266.00  
  Purchase #6 $6.71   13.795%   $7.6356   $7.64   $7.65   $7.60  
  Purchase #7 $150.36   11.357%   $167.4364   $167.44   $167.45   $167.40  
  7 purchase totals = $1,096.41       $1,200.7274   $1,200.73   $1,200.75   $1,200.70